Merge 862378ee24 into 7114435533

Drop Swift 5.9 (#235 )
Motivation: Swift 5.9 is no longer supported, we should bump the tools version and remove it from our CI. Modifications: * Bump the Swift tools version to Swift 5.10 * Remove Swift 5.9 jobs where appropriate in main.yml, pull_request.yml Result: Code reflects our support window.
2025-05-05 23:27:13 +00:00 · 2025-05-05 12:13:58 +01:00 · 2025-04-29 13:56:21 +01:00 · 2025-04-16 14:33:56 +01:00 · 2025-04-14 10:52:43 +01:00 · 2025-04-09 15:08:12 +01:00
30 changed files with 1069 additions and 491 deletions
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@ -11,8 +11,15 @@ jobs:
        name: Unit tests
        uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
        with:
-            linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
            linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
            linux_6_0_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
+            linux_6_1_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
            linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
            linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
+
+    macos-tests:
+        name: macOS tests
+        uses: apple/swift-nio/.github/workflows/macos_tests.yml@main
+        with:
+            runner_pool: nightly
+            build_scheme: swift-nio-transport-services-Package
--- a/.github/workflows/pull_request.yml
+++ b/.github/workflows/pull_request.yml
@ -14,12 +14,19 @@ jobs:
        name: Unit tests
        uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
        with:
-            linux_5_9_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
            linux_5_10_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error"
            linux_6_0_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
+            linux_6_1_arguments_override: "-Xswiftc -warnings-as-errors --explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
            linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
            linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"

    cxx-interop:
        name: Cxx interop
        uses: apple/swift-nio/.github/workflows/cxx_interop.yml@main
+
+    macos-tests:
+        name: macOS tests
+        uses: apple/swift-nio/.github/workflows/macos_tests.yml@main
+        with:
+            runner_pool: general
+            build_scheme: swift-nio-transport-services-Package
--- a/Package.swift
+++ b/Package.swift
@ -1,4 +1,4 @@
-// swift-tools-version:5.8
+// swift-tools-version:5.10
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the SwiftNIO open source project
@ -15,13 +15,31 @@

 import PackageDescription

+let strictConcurrencyDevelopment = false
+
+let strictConcurrencySettings: [SwiftSetting] = {
+    var initialSettings: [SwiftSetting] = []
+    initialSettings.append(contentsOf: [
+        .enableUpcomingFeature("StrictConcurrency"),
+        .enableUpcomingFeature("InferSendableFromCaptures"),
+    ])
+
+    if strictConcurrencyDevelopment {
+        // -warnings-as-errors here is a workaround so that IDE-based development can
+        // get tripped up on -require-explicit-sendable.
+        initialSettings.append(.unsafeFlags(["-Xfrontend", "-require-explicit-sendable", "-warnings-as-errors"]))
+    }
+
+    return initialSettings
+}()
+
 let package = Package(
    name: "swift-nio-transport-services",
    products: [
        .library(name: "NIOTransportServices", targets: ["NIOTransportServices"])
    ],
    dependencies: [
-        .package(url: "https://github.com/apple/swift-nio.git", from: "2.62.0"),
+        .package(url: "https://github.com/apple/swift-nio.git", from: "2.81.0"),
        .package(url: "https://github.com/apple/swift-atomics.git", from: "1.0.2"),
    ],
    targets: [
@ -33,7 +51,8 @@ let package = Package(
                .product(name: "NIOFoundationCompat", package: "swift-nio"),
                .product(name: "NIOTLS", package: "swift-nio"),
                .product(name: "Atomics", package: "swift-atomics"),
-            ]
+            ],
+            swiftSettings: strictConcurrencySettings
        ),
        .executableTarget(
            name: "NIOTSHTTPClient",
@ -58,7 +77,8 @@ let package = Package(
                .product(name: "NIOCore", package: "swift-nio"),
                .product(name: "NIOEmbedded", package: "swift-nio"),
                .product(name: "Atomics", package: "swift-atomics"),
-            ]
+            ],
+            swiftSettings: strictConcurrencySettings
        ),
    ]
 )
--- a/Sources/NIOTransportServices/AcceptHandler.swift
+++ b/Sources/NIOTransportServices/AcceptHandler.swift
@ -20,11 +20,11 @@ internal class AcceptHandler<ChildChannel: Channel>: ChannelInboundHandler {
    typealias InboundIn = ChildChannel
    typealias InboundOut = ChildChannel

-    private let childChannelInitializer: ((Channel) -> EventLoopFuture<Void>)?
+    private let childChannelInitializer: (@Sendable (Channel) -> EventLoopFuture<Void>)?
    private let childChannelOptions: ChannelOptions.Storage

    init(
-        childChannelInitializer: ((Channel) -> EventLoopFuture<Void>)?,
+        childChannelInitializer: (@Sendable (Channel) -> EventLoopFuture<Void>)?,
        childChannelOptions: ChannelOptions.Storage
    ) {
        self.childChannelInitializer = childChannelInitializer
@ -35,11 +35,12 @@ internal class AcceptHandler<ChildChannel: Channel>: ChannelInboundHandler {
        let newChannel = self.unwrapInboundIn(data)
        let childLoop = newChannel.eventLoop
        let ctxEventLoop = context.eventLoop
-        let childInitializer = self.childChannelInitializer ?? { _ in childLoop.makeSucceededFuture(()) }
+        let childInitializer = self.childChannelInitializer ?? { @Sendable _ in childLoop.makeSucceededFuture(()) }
+        let childChannelOptions = self.childChannelOptions

-        @inline(__always)
+        @Sendable @inline(__always)
        func setupChildChannel() -> EventLoopFuture<Void> {
-            self.childChannelOptions.applyAllChannelOptions(to: newChannel).flatMap { () -> EventLoopFuture<Void> in
+            childChannelOptions.applyAllChannelOptions(to: newChannel).flatMap { () -> EventLoopFuture<Void> in
                childLoop.assertInEventLoop()
                return childInitializer(newChannel)
            }
@ -48,8 +49,8 @@ internal class AcceptHandler<ChildChannel: Channel>: ChannelInboundHandler {
        @inline(__always)
        func fireThroughPipeline(_ future: EventLoopFuture<Void>) {
            ctxEventLoop.assertInEventLoop()
-            future.flatMap { (_) -> EventLoopFuture<Void> in
-                ctxEventLoop.assertInEventLoop()
+            assert(ctxEventLoop === context.eventLoop)
+            future.assumeIsolated().flatMap { (_) -> EventLoopFuture<Void> in
                guard context.channel.isActive else {
                    return newChannel.close().flatMapThrowing {
                        throw ChannelError.ioOnClosedChannel
@ -75,4 +76,7 @@ internal class AcceptHandler<ChildChannel: Channel>: ChannelInboundHandler {
        }
    }
 }
+
+@available(*, unavailable)
+extension AcceptHandler: Sendable {}
 #endif
--- a/Sources/NIOTransportServices/Datagram/NIOTSDatagramConnectionBootstrap.swift
+++ b/Sources/NIOTransportServices/Datagram/NIOTSDatagramConnectionBootstrap.swift
@ -17,9 +17,13 @@ import NIOCore
 import Dispatch
 import Network

-/// A `NIOTSDatagramBootstrap` is an easy way to bootstrap a `NIOTSDatagramChannel` when creating network clients.
+@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
+public typealias NIOTSDatagramBootstrap = NIOTSDatagramConnectionBootstrap
+
+/// A ``NIOTSDatagramConnectionBootstrap`` is an easy way to bootstrap a UDP channel when creating network clients.
 ///
-/// Usually you re-use a `NIOTSDatagramBootstrap` once you set it up, calling `connect` multiple times on the same bootstrap.
+/// Usually you re-use a ``NIOTSDatagramConnectionBootstrap`` once you set it up, calling `connect` multiple times on the
+/// same bootstrap.
 /// This way you ensure that the same `EventLoop`s will be shared across all your connections.
 ///
 /// Example:
@ -29,7 +33,7 @@ import Network
 ///     defer {
 ///         try! group.syncShutdownGracefully()
 ///     }
-///     let bootstrap = NIOTSDatagramBootstrap(group: group)
+///     let bootstrap = NIOTSDatagramConnectionBootstrap(group: group)
 ///         .channelInitializer { channel in
 ///             channel.pipeline.addHandler(MyChannelHandler())
 ///         }
@ -37,16 +41,17 @@ import Network
 ///     /* the Channel is now connected */
 /// ```
 ///
-/// The connected `NIOTSDatagramChannel` will operate on `ByteBuffer` as inbound and outbound messages.
+/// The connected channel will operate on `ByteBuffer` as inbound and outbound messages.
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-public final class NIOTSDatagramBootstrap {
+public final class NIOTSDatagramConnectionBootstrap {
    private let group: EventLoopGroup
-    private var channelInitializer: ((Channel) -> EventLoopFuture<Void>)?
+    private var channelInitializer: (@Sendable (Channel) -> EventLoopFuture<Void>)?
    private var connectTimeout: TimeAmount = TimeAmount.seconds(10)
    private var channelOptions = ChannelOptions.Storage()
    private var qos: DispatchQoS?
    private var udpOptions: NWProtocolUDP.Options = .init()
    private var tlsOptions: NWProtocolTLS.Options?
+    private var nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?

    /// Create a `NIOTSDatagramConnectionBootstrap` on the `EventLoopGroup` `group`.
    ///
@ -72,19 +77,20 @@ public final class NIOTSDatagramBootstrap {
        self.init(group: group as EventLoopGroup)
    }

-    /// Initialize the connected `NIOTSDatagramConnectionChannel` with `initializer`. The most common task in initializer is to add
+    /// Initialize the connected channel with `initializer`. The most common task in initializer is to add
    /// `ChannelHandler`s to the `ChannelPipeline`.
    ///
    /// The connected `Channel` will operate on `ByteBuffer` as inbound and outbound messages.
    ///
    /// - parameters:
    ///     - handler: A closure that initializes the provided `Channel`.
-    public func channelInitializer(_ handler: @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
+    @preconcurrency
+    public func channelInitializer(_ handler: @Sendable @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
        self.channelInitializer = handler
        return self
    }

-    /// Specifies a `ChannelOption` to be applied to the `NIOTSDatagramConnectionChannel`.
+    /// Specifies a `ChannelOption` to be applied to the channel.
    ///
    /// - parameters:
    ///     - option: The option to be applied.
@ -132,6 +138,14 @@ public final class NIOTSDatagramBootstrap {
        return self
    }

+    /// Customise the `NWParameters` to be used when creating the connection.
+    public func configureNWParameters(
+        _ configurator: @Sendable @escaping (NWParameters) -> Void
+    ) -> Self {
+        self.nwParametersConfigurator = configurator
+        return self
+    }
+
    /// Specify the `host` and `port` to connect to for the UDP `Channel` that will be established.
    ///
    /// - parameters:
@ -180,17 +194,19 @@ public final class NIOTSDatagramBootstrap {
        }
    }

-    private func connect0(_ binder: @escaping (Channel, EventLoopPromise<Void>) -> Void) -> EventLoopFuture<Channel> {
-        let conn: Channel = NIOTSDatagramChannel(
+    private func connect0(
+        _ binder: @Sendable @escaping (Channel, EventLoopPromise<Void>) -> Void
+    ) -> EventLoopFuture<Channel> {
+        let conn: Channel = NIOTSDatagramConnectionChannel(
            eventLoop: self.group.next() as! NIOTSEventLoop,
            qos: self.qos,
            udpOptions: self.udpOptions,
-            tlsOptions: self.tlsOptions
+            tlsOptions: self.tlsOptions,
+            nwParametersConfigurator: self.nwParametersConfigurator
        )
-        let initializer = self.channelInitializer ?? { _ in conn.eventLoop.makeSucceededFuture(()) }
-        let channelOptions = self.channelOptions
+        let initializer = self.channelInitializer ?? { @Sendable _ in conn.eventLoop.makeSucceededFuture(()) }

-        return conn.eventLoop.submit {
+        return conn.eventLoop.submit { [channelOptions, connectTimeout] in
            channelOptions.applyAllChannelOptions(to: conn).flatMap {
                initializer(conn)
            }.flatMap {
@ -199,8 +215,8 @@ public final class NIOTSDatagramBootstrap {
            }.flatMap {
                let connectPromise: EventLoopPromise<Void> = conn.eventLoop.makePromise()
                binder(conn, connectPromise)
-                let cancelTask = conn.eventLoop.scheduleTask(in: self.connectTimeout) {
-                    connectPromise.fail(ChannelError.connectTimeout(self.connectTimeout))
+                let cancelTask = conn.eventLoop.scheduleTask(in: connectTimeout) {
+                    connectPromise.fail(ChannelError.connectTimeout(connectTimeout))
                    conn.close(promise: nil)
                }

@ -215,4 +231,7 @@ public final class NIOTSDatagramBootstrap {
        }.flatMap { $0 }
    }
 }
+
+@available(*, unavailable)
+extension NIOTSDatagramConnectionBootstrap: Sendable {}
 #endif
--- a/Sources/NIOTransportServices/Datagram/NIOTSDatagramConnectionChannel.swift
+++ b/Sources/NIOTransportServices/Datagram/NIOTSDatagramConnectionChannel.swift
@ -24,7 +24,7 @@ import Network
 import Security

@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-internal final class NIOTSDatagramChannel: StateManagedNWConnectionChannel {
+internal final class NIOTSDatagramConnectionChannel: StateManagedNWConnectionChannel {
    typealias ActiveSubstate = UDPSubstate

    enum UDPSubstate: NWConnectionSubstate {
@ -34,11 +34,11 @@ internal final class NIOTSDatagramChannel: StateManagedNWConnectionChannel {
            self = .open
        }

-        static func closeInput(state: inout ChannelState<NIOTSDatagramChannel.UDPSubstate>) throws {
+        static func closeInput(state: inout ChannelState<NIOTSDatagramConnectionChannel.UDPSubstate>) throws {
            throw NIOTSErrors.InvalidChannelStateTransition()
        }

-        static func closeOutput(state: inout ChannelState<NIOTSDatagramChannel.UDPSubstate>) throws {
+        static func closeOutput(state: inout ChannelState<NIOTSDatagramConnectionChannel.UDPSubstate>) throws {
            throw NIOTSErrors.InvalidChannelStateTransition()
        }
    }
@ -140,8 +140,12 @@ internal final class NIOTSDatagramChannel: StateManagedNWConnectionChannel {
    internal var allowLocalEndpointReuse = false
    internal var multipathServiceType: NWParameters.MultipathServiceType = .disabled

+    internal let nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
+
    var parameters: NWParameters {
-        NWParameters(dtls: self.tlsOptions, udp: self.udpOptions)
+        let parameters = NWParameters(dtls: self.tlsOptions, udp: self.udpOptions)
+        self.nwParametersConfigurator?(parameters)
+        return parameters
    }

    var _inboundStreamOpen: Bool {
@ -182,7 +186,8 @@ internal final class NIOTSDatagramChannel: StateManagedNWConnectionChannel {
        minimumIncompleteReceiveLength: Int = 1,
        maximumReceiveLength: Int = 8192,
        udpOptions: NWProtocolUDP.Options,
-        tlsOptions: NWProtocolTLS.Options?
+        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.tsEventLoop = eventLoop
        self.closePromise = eventLoop.makePromise()
@ -192,6 +197,7 @@ internal final class NIOTSDatagramChannel: StateManagedNWConnectionChannel {
        self.connectionQueue = eventLoop.channelQueue(label: "nio.nioTransportServices.connectionchannel", qos: qos)
        self.udpOptions = udpOptions
        self.tlsOptions = tlsOptions
+        self.nwParametersConfigurator = nwParametersConfigurator

        // Must come last, as it requires self to be completely initialized.
        self._pipeline = ChannelPipeline(channel: self)
@ -206,7 +212,8 @@ internal final class NIOTSDatagramChannel: StateManagedNWConnectionChannel {
        minimumIncompleteReceiveLength: Int = 1,
        maximumReceiveLength: Int = 8192,
        udpOptions: NWProtocolUDP.Options,
-        tlsOptions: NWProtocolTLS.Options?
+        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.init(
            eventLoop: eventLoop,
@ -215,18 +222,19 @@ internal final class NIOTSDatagramChannel: StateManagedNWConnectionChannel {
            minimumIncompleteReceiveLength: minimumIncompleteReceiveLength,
            maximumReceiveLength: maximumReceiveLength,
            udpOptions: udpOptions,
-            tlsOptions: tlsOptions
+            tlsOptions: tlsOptions,
+            nwParametersConfigurator: nwParametersConfigurator
        )
        self.connection = connection
    }
 }

@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-extension NIOTSDatagramChannel {
+extension NIOTSDatagramConnectionChannel {
    internal struct SynchronousOptions: NIOSynchronousChannelOptions {
-        private let channel: NIOTSDatagramChannel
+        private let channel: NIOTSDatagramConnectionChannel

-        fileprivate init(channel: NIOTSDatagramChannel) {
+        fileprivate init(channel: NIOTSDatagramConnectionChannel) {
            self.channel = channel
        }

@ -243,4 +251,7 @@ extension NIOTSDatagramChannel {
        SynchronousOptions(channel: self)
    }
 }
+
+@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
+extension NIOTSDatagramConnectionChannel: @unchecked Sendable {}
 #endif
--- a/Sources/NIOTransportServices/Datagram/NIOTSDatagramListenerBootstrap.swift
+++ b/Sources/NIOTransportServices/Datagram/NIOTSDatagramListenerBootstrap.swift
@ -17,7 +17,7 @@ import NIOCore
 import Dispatch
 import Network

-/// A ``NIOTSListenerBootstrap`` is an easy way to bootstrap a `NIOTSListenerChannel` when creating network servers.
+/// A ``NIOTSDatagramListenerBootstrap`` is an easy way to bootstrap a listener channel when creating network servers.
 ///
 /// Example:
 ///
@ -26,7 +26,7 @@ import Network
 ///     defer {
 ///         try! group.syncShutdownGracefully()
 ///     }
-///     let bootstrap = NIOTSListenerBootstrap(group: group)
+///     let bootstrap = NIOTSDatagramListenerBootstrap(group: group)
 ///         // Specify backlog and enable SO_REUSEADDR for the server itself
 ///         .serverChannelOption(ChannelOptions.backlog, value: 256)
 ///         .serverChannelOption(ChannelOptions.socketOption(.reuseaddr), value: 1)
@ -46,28 +46,31 @@ import Network
 ///     try! channel.closeFuture.wait() // wait forever as we never close the Channel
 /// ```
 ///
-/// The `EventLoopFuture` returned by `bind` will fire with a `NIOTSListenerChannel`. This is the channel that owns the
-/// listening socket. Each time it accepts a new connection it will fire a `NIOTSConnectionChannel` through the
-/// `ChannelPipeline` via `fireChannelRead`: as a result, the `NIOTSListenerChannel` operates on `Channel`s as inbound
-/// messages. Outbound messages are not supported on a `NIOTSListenerChannel` which means that each write attempt will
-/// fail.
+/// The `EventLoopFuture` returned by `bind` will fire with a channel. This is the channel that owns the listening socket. Each
+/// time it accepts a new connection it will fire a new child channel for the new connection through the `ChannelPipeline` via
+/// `fireChannelRead`: as a result, the listening channel operates on `Channel`s as inbound messages. Outbound messages are
+/// not supported on these listening channels, which means that each write attempt will fail.
 ///
-/// Accepted `NIOTSConnectionChannel`s operate on `ByteBuffer` as inbound data, and `IOData` as outbound data.
+/// Accepted channels operate on `ByteBuffer` as inbound data, and `IOData` as outbound data.
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
 public final class NIOTSDatagramListenerBootstrap {
    private let group: EventLoopGroup
    private let childGroup: EventLoopGroup
-    private var serverChannelInit: ((Channel) -> EventLoopFuture<Void>)?
-    private var childChannelInit: ((Channel) -> EventLoopFuture<Void>)?
+    private var serverChannelInit: (@Sendable (Channel) -> EventLoopFuture<Void>)?
+    private var childChannelInit: (@Sendable (Channel) -> EventLoopFuture<Void>)?
    private var serverChannelOptions = ChannelOptions.Storage()
    private var childChannelOptions = ChannelOptions.Storage()
    private var serverQoS: DispatchQoS?
    private var childQoS: DispatchQoS?
    private var udpOptions: NWProtocolUDP.Options = .init()
+    private var childUDPOptions: NWProtocolUDP.Options = .init()
    private var tlsOptions: NWProtocolTLS.Options?
+    private var childTLSOptions: NWProtocolTLS.Options?
    private var bindTimeout: TimeAmount?
+    private var nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
+    private var childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?

-    /// Create a ``NIOTSListenerBootstrap`` for the `EventLoopGroup` `group`.
+    /// Create a ``NIOTSDatagramListenerBootstrap`` for the `EventLoopGroup` `group`.
    ///
    /// This initializer only exists to be more in-line with the NIO core bootstraps, in that they
    /// may be constructed with an `EventLoopGroup` and by extension an `EventLoop`. As such an
@ -78,20 +81,20 @@ public final class NIOTSDatagramListenerBootstrap {
    /// > Note: The "real" solution is described in https://github.com/apple/swift-nio/issues/674.
    ///
    /// - parameters:
-    ///     - group: The `EventLoopGroup` to use for the `NIOTSListenerChannel`.
+    ///     - group: The `EventLoopGroup` to use for the listening channel.
    public convenience init(group: EventLoopGroup) {
        self.init(group: group, childGroup: group)
    }

-    /// Create a ``NIOTSListenerBootstrap`` for the ``NIOTSEventLoopGroup`` `group`.
+    /// Create a ``NIOTSDatagramListenerBootstrap`` for the ``NIOTSEventLoopGroup`` `group`.
    ///
    /// - parameters:
-    ///     - group: The ``NIOTSEventLoopGroup`` to use for the `NIOTSListenerChannel`.
+    ///     - group: The ``NIOTSEventLoopGroup`` to use for the listening channel.
    public convenience init(group: NIOTSEventLoopGroup) {
        self.init(group: group as EventLoopGroup)
    }

-    /// Create a ``NIOTSListenerBootstrap``.
+    /// Create a ``NIOTSDatagramListenerBootstrap``.
    ///
    /// This initializer only exists to be more in-line with the NIO core bootstraps, in that they
    /// may be constructed with an `EventLoopGroup` and by extension an `EventLoop`. As such an
@ -102,9 +105,8 @@ public final class NIOTSDatagramListenerBootstrap {
    /// > Note: The "real" solution is described in https://github.com/apple/swift-nio/issues/674.
    ///
    /// - parameters:
-    ///     - group: The `EventLoopGroup` to use for the `bind` of the `NIOTSListenerChannel`
-    ///         and to accept new `NIOTSConnectionChannel`s with.
-    ///     - childGroup: The `EventLoopGroup` to run the accepted `NIOTSConnectionChannel`s on.
+    ///     - group: The `EventLoopGroup` to use for the `bind` of the listening channel and to accept new child channels with.
+    ///     - childGroup: The `EventLoopGroup` to run the accepted child channels on.
    public convenience init(group: EventLoopGroup, childGroup: EventLoopGroup) {
        guard NIOTSBootstraps.isCompatible(group: group) && NIOTSBootstraps.isCompatible(group: childGroup) else {
            preconditionFailure(
@ -117,13 +119,12 @@ public final class NIOTSDatagramListenerBootstrap {
        self.init(validatingGroup: group, childGroup: childGroup)!
    }

-    /// Create a ``NIOTSListenerBootstrap`` on the `EventLoopGroup` `group` which accepts `Channel`s on `childGroup`,
-    /// validating that the `EventLoopGroup`s are compatible with ``NIOTSListenerBootstrap``.
+    /// Create a ``NIOTSDatagramListenerBootstrap`` on the `EventLoopGroup` `group` which accepts `Channel`s
+    /// on `childGroup`, validating that the `EventLoopGroup`s are compatible with ``NIOTSDatagramListenerBootstrap``.
    ///
    /// - parameters:
-    ///     - group: The `EventLoopGroup` to use for the `bind` of the `NIOTSListenerChannel`
-    ///         and to accept new `NIOTSConnectionChannel`s with.
-    ///     - childGroup: The `EventLoopGroup` to run the accepted `NIOTSConnectionChannel`s on.
+    ///     - group: The `EventLoopGroup` to use for the `bind` of the listening channel and to accept new child channels with.
+    ///     - childGroup: The `EventLoopGroup` to run the accepted child channels on.
    public init?(validatingGroup group: EventLoopGroup, childGroup: EventLoopGroup? = nil) {
        let childGroup = childGroup ?? group
        guard NIOTSBootstraps.isCompatible(group: group) && NIOTSBootstraps.isCompatible(group: childGroup) else {
@ -134,32 +135,33 @@ public final class NIOTSDatagramListenerBootstrap {
        self.childGroup = childGroup
    }

-    /// Create a ``NIOTSListenerBootstrap``.
+    /// Create a ``NIOTSDatagramListenerBootstrap``.
    ///
    /// - parameters:
-    ///     - group: The ``NIOTSEventLoopGroup`` to use for the `bind` of the `NIOTSListenerChannel`
-    ///         and to accept new `NIOTSConnectionChannel`s with.
-    ///     - childGroup: The ``NIOTSEventLoopGroup`` to run the accepted `NIOTSConnectionChannel`s on.
+    ///     - group: The ``NIOTSEventLoopGroup`` to use for the `bind` of the listening channel and to accept new child
+    ///     channels with.
+    ///     - childGroup: The ``NIOTSEventLoopGroup`` to run the accepted child channels on.
    public convenience init(group: NIOTSEventLoopGroup, childGroup: NIOTSEventLoopGroup) {
        self.init(group: group as EventLoopGroup, childGroup: childGroup as EventLoopGroup)
    }

-    /// Initialize the `NIOTSListenerChannel` with `initializer`. The most common task in initializer is to add
+    /// Initialize the listening channel with `initializer`. The most common task in initializer is to add
    /// `ChannelHandler`s to the `ChannelPipeline`.
    ///
-    /// The `NIOTSListenerChannel` uses the accepted `NIOTSConnectionChannel`s as inbound messages.
+    /// The listening channel uses the accepted child channels as inbound messages.
    ///
-    /// > Note: To set the initializer for the accepted `NIOTSConnectionChannel`s, look at
-    ///     ``childChannelInitializer(_:)``.
+    /// > Note: To set the initializer for the accepted child channels, look at ``childChannelInitializer(_:)``.
    ///
    /// - parameters:
    ///     - initializer: A closure that initializes the provided `Channel`.
-    public func serverChannelInitializer(_ initializer: @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
+    @preconcurrency
+    public func serverChannelInitializer(_ initializer: @Sendable @escaping (Channel) -> EventLoopFuture<Void>) -> Self
+    {
        self.serverChannelInit = initializer
        return self
    }

-    /// Initialize the accepted `NIOTSConnectionChannel`s with `initializer`. The most common task in initializer is to add
+    /// Initialize the accepted child channels with `initializer`. The most common task in initializer is to add
    /// `ChannelHandler`s to the `ChannelPipeline`. Note that if the `initializer` fails then the error will be
    /// fired in the *parent* channel.
    ///
@ -167,14 +169,15 @@ public final class NIOTSDatagramListenerBootstrap {
    ///
    /// - parameters:
    ///     - initializer: A closure that initializes the provided `Channel`.
-    public func childChannelInitializer(_ initializer: @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
+    @preconcurrency
+    public func childChannelInitializer(_ initializer: @Sendable @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
        self.childChannelInit = initializer
        return self
    }

-    /// Specifies a `ChannelOption` to be applied to the `NIOTSListenerChannel`.
+    /// Specifies a `ChannelOption` to be applied to the listening channel.
    ///
-    /// > Note: To specify options for the accepted `NIOTSConnectionChannel`s, look at ``childChannelOption(_:value:)``.
+    /// > Note: To specify options for the accepted child channels, look at ``childChannelOption(_:value:)``.
    ///
    /// - parameters:
    ///     - option: The option to be applied.
@ -184,7 +187,7 @@ public final class NIOTSDatagramListenerBootstrap {
        return self
    }

-    /// Specifies a `ChannelOption` to be applied to the accepted `NIOTSConnectionChannel`s.
+    /// Specifies a `ChannelOption` to be applied to the accepted child channels.
    ///
    /// - parameters:
    ///     - option: The option to be applied.
@ -221,19 +224,47 @@ public final class NIOTSDatagramListenerBootstrap {
        return self
    }

-    /// Specifies the TCP options to use on the child `Channel`s.
+    /// Specifies the TCP options to use on the listener.
    public func udpOptions(_ options: NWProtocolUDP.Options) -> Self {
        self.udpOptions = options
        return self
    }

-    /// Specifies the TLS options to use on the child `Channel`s.
+    /// Specifies the TCP options to use on the child `Channel`s.
+    public func childUDPOptions(_ options: NWProtocolUDP.Options) -> Self {
+        self.childUDPOptions = options
+        return self
+    }
+
+    /// Specifies the TLS options to use on the listener.
    public func tlsOptions(_ options: NWProtocolTLS.Options) -> Self {
        self.tlsOptions = options
        return self
    }

-    /// Bind the `NIOTSListenerChannel` to `host` and `port`.
+    /// Specifies the TLS options to use on the child `Channel`s.
+    public func childTLSOptions(_ options: NWProtocolTLS.Options) -> Self {
+        self.childTLSOptions = options
+        return self
+    }
+
+    /// Customise the `NWParameters` to be used when creating the `NWConnection` for the listener.
+    public func configureNWParameters(
+        _ configurator: @Sendable @escaping (NWParameters) -> Void
+    ) -> Self {
+        self.nwParametersConfigurator = configurator
+        return self
+    }
+
+    /// Customise the `NWParameters` to be used when creating the `NWConnection`s for the child `Channel`s.
+    public func configureChildNWParameters(
+        _ configurator: @Sendable @escaping (NWParameters) -> Void
+    ) -> Self {
+        self.childNWParametersConfigurator = configurator
+        return self
+    }
+
+    /// Bind the listening channel to `host` and `port`.
    ///
    /// - parameters:
    ///     - host: The host to bind on.
@ -257,7 +288,7 @@ public final class NIOTSDatagramListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to `address`.
+    /// Bind the listening channel to `address`.
    ///
    /// - parameters:
    ///     - address: The `SocketAddress` to bind on.
@ -267,7 +298,7 @@ public final class NIOTSDatagramListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to a UNIX Domain Socket.
+    /// Bind the listening channel to a UNIX Domain Socket.
    ///
    /// - parameters:
    ///     - unixDomainSocketPath: The _Unix domain socket_ path to bind to. `unixDomainSocketPath` must not exist, it will be created by the system.
@ -282,7 +313,7 @@ public final class NIOTSDatagramListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to a given `NWEndpoint`.
+    /// Bind the listening channel to a given `NWEndpoint`.
    ///
    /// - parameters:
    ///     - endpoint: The `NWEndpoint` to bind this channel to.
@ -292,7 +323,7 @@ public final class NIOTSDatagramListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to an existing `NWListener`.
+    /// Bind the listening channel to an existing `NWListener`.
    ///
    /// - parameters:
    ///     - listener: The NWListener to wrap.
@ -305,10 +336,13 @@ public final class NIOTSDatagramListenerBootstrap {
    private func bind0(
        existingNWListener: NWListener? = nil,
        shouldRegister: Bool,
-        _ binder: @escaping (NIOTSDatagramListenerChannel, EventLoopPromise<Void>) -> Void
+        _ binder: @Sendable @escaping (NIOTSDatagramListenerChannel, EventLoopPromise<Void>) -> Void
    ) -> EventLoopFuture<Channel> {
        let eventLoop = self.group.next() as! NIOTSEventLoop
-        let serverChannelInit = self.serverChannelInit ?? { _ in eventLoop.makeSucceededFuture(()) }
+        let serverChannelInit =
+            self.serverChannelInit ?? {
+                @Sendable _ in eventLoop.makeSucceededFuture(())
+            }
        let childChannelInit = self.childChannelInit
        let serverChannelOptions = self.serverChannelOptions
        let childChannelOptions = self.childChannelOptions
@ -321,10 +355,12 @@ public final class NIOTSDatagramListenerBootstrap {
                qos: self.serverQoS,
                udpOptions: self.udpOptions,
                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator,
                childLoopGroup: self.childGroup,
                childChannelQoS: self.childQoS,
-                childUDPOptions: self.udpOptions,
-                childTLSOptions: self.tlsOptions
+                childUDPOptions: self.childUDPOptions,
+                childTLSOptions: self.childTLSOptions,
+                childNWParametersConfigurator: self.childNWParametersConfigurator
            )
        } else {
            serverChannel = NIOTSDatagramListenerChannel(
@ -332,24 +368,28 @@ public final class NIOTSDatagramListenerBootstrap {
                qos: self.serverQoS,
                udpOptions: self.udpOptions,
                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator,
                childLoopGroup: self.childGroup,
                childChannelQoS: self.childQoS,
-                childUDPOptions: self.udpOptions,
-                childTLSOptions: self.tlsOptions
+                childUDPOptions: self.childUDPOptions,
+                childTLSOptions: self.childTLSOptions,
+                childNWParametersConfigurator: self.childNWParametersConfigurator
            )
        }

-        return eventLoop.submit {
+        return eventLoop.submit { [bindTimeout] in
            serverChannelOptions.applyAllChannelOptions(to: serverChannel).flatMap {
                serverChannelInit(serverChannel)
            }.flatMap {
                eventLoop.assertInEventLoop()
-                return serverChannel.pipeline.addHandler(
-                    AcceptHandler<NIOTSDatagramChannel>(
+                return eventLoop.makeCompletedFuture {
+                    try serverChannel.pipeline.syncOperations.addHandler(
+                        AcceptHandler<NIOTSDatagramConnectionChannel>(
                            childChannelInitializer: childChannelInit,
                            childChannelOptions: childChannelOptions
                        )
                    )
+                }
            }.flatMap {
                if shouldRegister {
                    return serverChannel.register()
@ -360,7 +400,7 @@ public final class NIOTSDatagramListenerBootstrap {
                let bindPromise = eventLoop.makePromise(of: Void.self)
                binder(serverChannel, bindPromise)

-                if let bindTimeout = self.bindTimeout {
+                if let bindTimeout = bindTimeout {
                    let cancelTask = eventLoop.scheduleTask(in: bindTimeout) {
                        bindPromise.fail(NIOTSErrors.BindTimeout(timeout: bindTimeout))
                        serverChannel.close(promise: nil)
@ -382,4 +422,7 @@ public final class NIOTSDatagramListenerBootstrap {
        }
    }
 }
+
+@available(*, unavailable)
+extension NIOTSDatagramListenerBootstrap: Sendable {}
 #endif
--- a/Sources/NIOTransportServices/Datagram/NIOTSDatagramListenerChannel.swift
+++ b/Sources/NIOTransportServices/Datagram/NIOTSDatagramListenerChannel.swift
@ -22,7 +22,7 @@ import Network
 import Atomics

@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-internal final class NIOTSDatagramListenerChannel: StateManagedListenerChannel<NIOTSDatagramChannel> {
+internal final class NIOTSDatagramListenerChannel: StateManagedListenerChannel<NIOTSDatagramConnectionChannel> {
    /// The TCP options for this listener.
    private var udpOptions: NWProtocolUDP.Options {
        get {
@ -81,19 +81,23 @@ internal final class NIOTSDatagramListenerChannel: StateManagedListenerChannel<N
        qos: DispatchQoS? = nil,
        udpOptions: NWProtocolUDP.Options,
        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?,
        childLoopGroup: EventLoopGroup,
        childChannelQoS: DispatchQoS?,
        childUDPOptions: NWProtocolUDP.Options,
-        childTLSOptions: NWProtocolTLS.Options?
+        childTLSOptions: NWProtocolTLS.Options?,
+        childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.init(
            eventLoop: eventLoop,
            protocolOptions: .udp(udpOptions),
            tlsOptions: tlsOptions,
+            nwParametersConfigurator: nwParametersConfigurator,
            childLoopGroup: childLoopGroup,
            childChannelQoS: childChannelQoS,
            childProtocolOptions: .udp(childUDPOptions),
-            childTLSOptions: childTLSOptions
+            childTLSOptions: childTLSOptions,
+            childNWParametersConfigurator: childNWParametersConfigurator
        )
    }

@ -104,20 +108,24 @@ internal final class NIOTSDatagramListenerChannel: StateManagedListenerChannel<N
        qos: DispatchQoS? = nil,
        udpOptions: NWProtocolUDP.Options,
        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?,
        childLoopGroup: EventLoopGroup,
        childChannelQoS: DispatchQoS?,
        childUDPOptions: NWProtocolUDP.Options,
-        childTLSOptions: NWProtocolTLS.Options?
+        childTLSOptions: NWProtocolTLS.Options?,
+        childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.init(
            wrapping: listener,
            eventLoop: eventLoop,
            protocolOptions: .udp(udpOptions),
            tlsOptions: tlsOptions,
+            nwParametersConfigurator: nwParametersConfigurator,
            childLoopGroup: childLoopGroup,
            childChannelQoS: childChannelQoS,
            childProtocolOptions: .udp(childUDPOptions),
-            childTLSOptions: childTLSOptions
+            childTLSOptions: childTLSOptions,
+            childNWParametersConfigurator: childNWParametersConfigurator
        )
    }

@ -127,15 +135,16 @@ internal final class NIOTSDatagramListenerChannel: StateManagedListenerChannel<N
            return
        }

-        let newChannel = NIOTSDatagramChannel(
+        let newChannel = NIOTSDatagramConnectionChannel(
            wrapping: connection,
            on: self.childLoopGroup.next() as! NIOTSEventLoop,
            parent: self,
            udpOptions: self.childUDPOptions,
-            tlsOptions: self.childTLSOptions
+            tlsOptions: self.childTLSOptions,
+            nwParametersConfigurator: self.childNWParametersConfigurator
        )

-        self.pipeline.fireChannelRead(NIOAny(newChannel))
+        self.pipeline.fireChannelRead(newChannel)
        self.pipeline.fireChannelReadComplete()
    }

--- a/Sources/NIOTransportServices/NIOTSChannelOptions.swift
+++ b/Sources/NIOTransportServices/NIOTSChannelOptions.swift
@ -13,11 +13,11 @@
 //===----------------------------------------------------------------------===//
 #if canImport(Network)
 import NIOCore
-@preconcurrency import Network
+import Network

 /// Options that can be set explicitly and only on bootstraps provided by `NIOTransportServices`.
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-public struct NIOTSChannelOptions {
+public struct NIOTSChannelOptions: Sendable {
    /// See: ``Types/NIOTSWaitForActivityOption``.
    public static let waitForActivity = NIOTSChannelOptions.Types.NIOTSWaitForActivityOption()

@ -32,7 +32,7 @@ public struct NIOTSChannelOptions {

    /// See: ``Types/NIOTSMetadataOption``
    public static let metadata = {
-        (definition: NWProtocolDefinition) -> NIOTSChannelOptions.Types.NIOTSMetadataOption in
+        @Sendable (definition: NWProtocolDefinition) -> NIOTSChannelOptions.Types.NIOTSMetadataOption in
        .init(definition: definition)
    }

@ -66,7 +66,7 @@ public struct NIOTSChannelOptions {
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
 extension NIOTSChannelOptions {
    /// A namespace for ``NIOTSChannelOptions`` datastructures.
-    public enum Types {
+    public enum Types: Sendable {
        /// ``NIOTSWaitForActivityOption`` controls whether the `Channel` should wait for connection changes
        /// during the connection process if the connection attempt fails. If Network.framework believes that
        /// a connection may succeed in future, it may transition into the `.waiting` state. By default, this option
--- a/Sources/NIOTransportServices/NIOTSConnectionBootstrap.swift
+++ b/Sources/NIOTransportServices/NIOTSConnectionBootstrap.swift
@ -17,9 +17,9 @@ import NIOCore
 import Dispatch
 import Network

-/// A `NIOTSConnectionBootstrap` is an easy way to bootstrap a `NIOTSConnectionChannel` when creating network clients.
+/// A ``NIOTSConnectionBootstrap`` is an easy way to bootstrap a channel when creating network clients.
 ///
-/// Usually you re-use a `NIOTSConnectionBootstrap` once you set it up, calling `connect` multiple times on the same bootstrap.
+/// Usually you re-use a ``NIOTSConnectionBootstrap`` once you set it up, calling `connect` multiple times on the same bootstrap.
 /// This way you ensure that the same `EventLoop`s will be shared across all your connections.
 ///
 /// Example:
@ -37,17 +37,19 @@ import Network
 ///     /* the Channel is now connected */
 /// ```
 ///
-/// The connected `NIOTSConnectionChannel` will operate on `ByteBuffer` as inbound and on `IOData` as outbound messages.
+/// The connected channel will operate on `ByteBuffer` as inbound and on `IOData` as outbound messages.
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
 public final class NIOTSConnectionBootstrap {
    private let group: EventLoopGroup
-    private var _channelInitializer: ((Channel) -> EventLoopFuture<Void>)
-    private var channelInitializer: ((Channel) -> EventLoopFuture<Void>) {
+    private var _channelInitializer: (@Sendable (Channel) -> EventLoopFuture<Void>)
+    private var channelInitializer: (@Sendable (Channel) -> EventLoopFuture<Void>) {
        if let protocolHandlers = self.protocolHandlers {
            let channelInitializer = self._channelInitializer
            return { channel in
                channelInitializer(channel).flatMap {
-                    channel.pipeline.addHandlers(protocolHandlers(), position: .first)
+                    channel.eventLoop.makeCompletedFuture {
+                        try channel.pipeline.syncOperations.addHandlers(protocolHandlers(), position: .first)
+                    }
                }
            }
        } else {
@ -59,11 +61,12 @@ public final class NIOTSConnectionBootstrap {
    private var qos: DispatchQoS?
    private var tcpOptions: NWProtocolTCP.Options = .init()
    private var tlsOptions: NWProtocolTLS.Options?
-    private var protocolHandlers: (() -> [ChannelHandler])? = nil
+    private var protocolHandlers: (@Sendable () -> [ChannelHandler])? = nil
+    private var nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?

-    /// Create a `NIOTSConnectionBootstrap` on the `EventLoopGroup` `group`.
+    /// Create a ``NIOTSConnectionBootstrap`` on the `EventLoopGroup` `group`.
    ///
-    /// The `EventLoopGroup` `group` must be compatible, otherwise the program will crash. `NIOTSConnectionBootstrap` is
+    /// The `EventLoopGroup` `group` must be compatible, otherwise the program will crash. ``NIOTSConnectionBootstrap`` is
    /// compatible only with ``NIOTSEventLoopGroup`` as well as the `EventLoop`s returned by
    /// ``NIOTSEventLoopGroup/next()``. See ``init(validatingGroup:)`` for a fallible initializer for
    /// situations where it's impossible to tell ahead of time if the `EventLoopGroup` is compatible or not.
@ -81,7 +84,7 @@ public final class NIOTSConnectionBootstrap {
        self.init(validatingGroup: group)!
    }

-    /// Create a `NIOTSConnectionBootstrap` on the ``NIOTSEventLoopGroup`` `group`.
+    /// Create a ``NIOTSConnectionBootstrap`` on the ``NIOTSEventLoopGroup`` `group`.
    ///
    /// - parameters:
    ///     - group: The ``NIOTSEventLoopGroup`` to use.
@ -89,7 +92,7 @@ public final class NIOTSConnectionBootstrap {
        self.init(group: group as EventLoopGroup)
    }

-    /// Create a `NIOTSConnectionBootstrap` on the ``NIOTSEventLoopGroup`` `group`, validating
+    /// Create a ``NIOTSConnectionBootstrap`` on the ``NIOTSEventLoopGroup`` `group`, validating
    /// that the `EventLoopGroup` is compatible with ``NIOTSConnectionBootstrap``.
    ///
    /// - parameters:
@ -104,19 +107,20 @@ public final class NIOTSConnectionBootstrap {
        self._channelInitializer = { channel in channel.eventLoop.makeSucceededVoidFuture() }
    }

-    /// Initialize the connected `NIOTSConnectionChannel` with `initializer`. The most common task in initializer is to add
+    /// Initialize the connected channel with `initializer`. The most common task in initializer is to add
    /// `ChannelHandler`s to the `ChannelPipeline`.
    ///
    /// The connected `Channel` will operate on `ByteBuffer` as inbound and `IOData` as outbound messages.
    ///
    /// - parameters:
    ///     - handler: A closure that initializes the provided `Channel`.
-    public func channelInitializer(_ handler: @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
+    @preconcurrency
+    public func channelInitializer(_ handler: @escaping @Sendable (Channel) -> EventLoopFuture<Void>) -> Self {
        self._channelInitializer = handler
        return self
    }

-    /// Specifies a `ChannelOption` to be applied to the `NIOTSConnectionChannel`.
+    /// Specifies a `ChannelOption` to be applied to the channel.
    ///
    /// - parameters:
    ///     - option: The option to be applied.
@ -162,6 +166,14 @@ public final class NIOTSConnectionBootstrap {
        self.channelOption(NIOTSChannelOptions.multipathServiceType, value: type)
    }

+    /// Customise the `NWParameters` to be used when creating the connection.
+    public func configureNWParameters(
+        _ configurator: @Sendable @escaping (NWParameters) -> Void
+    ) -> Self {
+        self.nwParametersConfigurator = configurator
+        return self
+    }
+
    /// Specify the `host` and `port` to connect to for the TCP `Channel` that will be established.
    ///
    /// - parameters:
@ -229,7 +241,10 @@ public final class NIOTSConnectionBootstrap {
    private func connect(
        existingNWConnection: NWConnection? = nil,
        shouldRegister: Bool,
-        _ connectAction: @escaping (NIOTSConnectionChannel, EventLoopPromise<Void>) -> Void
+        _ connectAction: @Sendable @escaping (
+            NIOTSConnectionChannel,
+            EventLoopPromise<Void>
+        ) -> Void
    ) -> EventLoopFuture<Channel> {
        let conn: NIOTSConnectionChannel
        if let newConnection = existingNWConnection {
@ -237,20 +252,22 @@ public final class NIOTSConnectionBootstrap {
                wrapping: newConnection,
                on: self.group.next() as! NIOTSEventLoop,
                tcpOptions: self.tcpOptions,
-                tlsOptions: self.tlsOptions
+                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator
            )
        } else {
            conn = NIOTSConnectionChannel(
                eventLoop: self.group.next() as! NIOTSEventLoop,
                qos: self.qos,
                tcpOptions: self.tcpOptions,
-                tlsOptions: self.tlsOptions
+                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator
            )
        }
        let initializer = self.channelInitializer
        let channelOptions = self.channelOptions

-        return conn.eventLoop.flatSubmit {
+        return conn.eventLoop.flatSubmit { [connectTimeout] in
            channelOptions.applyAllChannelOptions(to: conn).flatMap {
                initializer(conn)
            }.flatMap {
@ -263,8 +280,8 @@ public final class NIOTSConnectionBootstrap {
            }.flatMap {
                let connectPromise: EventLoopPromise<Void> = conn.eventLoop.makePromise()
                connectAction(conn, connectPromise)
-                let cancelTask = conn.eventLoop.scheduleTask(in: self.connectTimeout) {
-                    connectPromise.fail(ChannelError.connectTimeout(self.connectTimeout))
+                let cancelTask = conn.eventLoop.scheduleTask(in: connectTimeout) {
+                    connectPromise.fail(ChannelError.connectTimeout(connectTimeout))
                    conn.close(promise: nil)
                }

@ -285,7 +302,8 @@ public final class NIOTSConnectionBootstrap {
    /// Per bootstrap, you can only set the `protocolHandlers` once. Typically, `protocolHandlers` are used for the TLS
    /// implementation. Most notably, `NIOClientTCPBootstrap`, NIO's "universal bootstrap" abstraction, uses
    /// `protocolHandlers` to add the required `ChannelHandler`s for many TLS implementations.
-    public func protocolHandlers(_ handlers: @escaping () -> [ChannelHandler]) -> Self {
+    @preconcurrency
+    public func protocolHandlers(_ handlers: @Sendable @escaping () -> [ChannelHandler]) -> Self {
        precondition(self.protocolHandlers == nil, "protocol handlers can only be set once")
        self.protocolHandlers = handlers
        return self
@ -419,10 +437,10 @@ extension NIOTSConnectionBootstrap {
    }

    @available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
-    private func connect0<ChannelInitializerResult>(
+    private func connect0<ChannelInitializerResult: Sendable>(
        existingNWConnection: NWConnection? = nil,
        channelInitializer: @escaping @Sendable (Channel) -> EventLoopFuture<ChannelInitializerResult>,
-        registration: @escaping (NIOTSConnectionChannel, EventLoopPromise<Void>) -> Void
+        registration: @Sendable @escaping (NIOTSConnectionChannel, EventLoopPromise<Void>) -> Void
    ) -> EventLoopFuture<ChannelInitializerResult> {
        let connectionChannel: NIOTSConnectionChannel
        if let newConnection = existingNWConnection {
@ -430,30 +448,32 @@ extension NIOTSConnectionBootstrap {
                wrapping: newConnection,
                on: self.group.next() as! NIOTSEventLoop,
                tcpOptions: self.tcpOptions,
-                tlsOptions: self.tlsOptions
+                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator
            )
        } else {
            connectionChannel = NIOTSConnectionChannel(
                eventLoop: self.group.next() as! NIOTSEventLoop,
                qos: self.qos,
                tcpOptions: self.tcpOptions,
-                tlsOptions: self.tlsOptions
+                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator
            )
        }
-        let channelInitializer = { (channel: Channel) -> EventLoopFuture<ChannelInitializerResult> in
        let initializer = self.channelInitializer
-            return initializer(channel).flatMap { channelInitializer(channel) }
+        let channelInitializer = { @Sendable (channel: Channel) -> EventLoopFuture<ChannelInitializerResult> in
+            initializer(channel).flatMap { channelInitializer(channel) }
        }
        let channelOptions = self.channelOptions

-        return connectionChannel.eventLoop.flatSubmit {
+        return connectionChannel.eventLoop.flatSubmit { [connectTimeout] in
            channelOptions.applyAllChannelOptions(to: connectionChannel).flatMap {
                channelInitializer(connectionChannel)
            }.flatMap { result -> EventLoopFuture<ChannelInitializerResult> in
                let connectPromise: EventLoopPromise<Void> = connectionChannel.eventLoop.makePromise()
                registration(connectionChannel, connectPromise)
-                let cancelTask = connectionChannel.eventLoop.scheduleTask(in: self.connectTimeout) {
-                    connectPromise.fail(ChannelError.connectTimeout(self.connectTimeout))
+                let cancelTask = connectionChannel.eventLoop.scheduleTask(in: connectTimeout) {
+                    connectPromise.fail(ChannelError.connectTimeout(connectTimeout))
                    connectionChannel.close(promise: nil)
                }

--- a/Sources/NIOTransportServices/NIOTSConnectionChannel.swift
+++ b/Sources/NIOTransportServices/NIOTSConnectionChannel.swift
@ -164,8 +164,12 @@ internal final class NIOTSConnectionChannel: StateManagedNWConnectionChannel {
    /// An `EventLoopPromise` that will be succeeded or failed when a connection attempt succeeds or fails.
    internal var connectPromise: EventLoopPromise<Void>?

+    internal let nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
+
    internal var parameters: NWParameters {
-        NWParameters(tls: self.tlsOptions, tcp: self.tcpOptions)
+        let parameters = NWParameters(tls: self.tlsOptions, tcp: self.tcpOptions)
+        self.nwParametersConfigurator?(parameters)
+        return parameters
    }

    /// The TCP options for this connection.
@ -242,7 +246,8 @@ internal final class NIOTSConnectionChannel: StateManagedNWConnectionChannel {
        minimumIncompleteReceiveLength: Int = 1,
        maximumReceiveLength: Int = 8192,
        tcpOptions: NWProtocolTCP.Options,
-        tlsOptions: NWProtocolTLS.Options?
+        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.tsEventLoop = eventLoop
        self.closePromise = eventLoop.makePromise()
@ -252,6 +257,7 @@ internal final class NIOTSConnectionChannel: StateManagedNWConnectionChannel {
        self.connectionQueue = eventLoop.channelQueue(label: "nio.nioTransportServices.connectionchannel", qos: qos)
        self.tcpOptions = tcpOptions
        self.tlsOptions = tlsOptions
+        self.nwParametersConfigurator = nwParametersConfigurator

        // Must come last, as it requires self to be completely initialized.
        self._pipeline = ChannelPipeline(channel: self)
@ -266,7 +272,8 @@ internal final class NIOTSConnectionChannel: StateManagedNWConnectionChannel {
        minimumIncompleteReceiveLength: Int = 1,
        maximumReceiveLength: Int = 8192,
        tcpOptions: NWProtocolTCP.Options,
-        tlsOptions: NWProtocolTLS.Options?
+        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.init(
            eventLoop: eventLoop,
@ -275,7 +282,8 @@ internal final class NIOTSConnectionChannel: StateManagedNWConnectionChannel {
            minimumIncompleteReceiveLength: minimumIncompleteReceiveLength,
            maximumReceiveLength: maximumReceiveLength,
            tcpOptions: tcpOptions,
-            tlsOptions: tlsOptions
+            tlsOptions: tlsOptions,
+            nwParametersConfigurator: nwParametersConfigurator
        )
        self.connection = connection
    }
@ -406,7 +414,7 @@ extension NIOTSConnectionChannel {
            // APIs.
            var buffer = self.allocator.buffer(capacity: content.count)
            buffer.writeBytes(content)
-            self.pipeline.fireChannelRead(NIOAny(buffer))
+            self.pipeline.fireChannelRead(buffer)
            self.pipeline.fireChannelReadComplete()
        }

@ -568,4 +576,7 @@ extension Channel {
    }
 }

+@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
+extension NIOTSConnectionChannel: @unchecked Sendable {}
+
 #endif
--- a/Sources/NIOTransportServices/NIOTSErrors.swift
+++ b/Sources/NIOTransportServices/NIOTSErrors.swift
@ -21,7 +21,7 @@ import NIOCore
 public protocol NIOTSError: Error, Equatable {}

@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-public enum NIOTSErrors {
+public enum NIOTSErrors: Sendable {
    /// ``InvalidChannelStateTransition`` is thrown when a channel has been asked to do something
    /// that is incompatible with its current channel state: e.g. attempting to register an
    /// already registered channel.
--- a/Sources/NIOTransportServices/NIOTSEventLoop.swift
+++ b/Sources/NIOTransportServices/NIOTSEventLoop.swift
@ -13,7 +13,11 @@
 //===----------------------------------------------------------------------===//

 #if canImport(Network)
-import Dispatch
+#if swift(<6.1)
+@preconcurrency import class Dispatch.DispatchSource
+#else
+import class Dispatch.DispatchSource
+#endif
 import Foundation
 import Network

@ -28,11 +32,17 @@ import NIOConcurrencyHelpers
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
 public protocol QoSEventLoop: EventLoop {
    /// Submit a given task to be executed by the `EventLoop` at a given `qos`.
-    func execute(qos: DispatchQoS, _ task: @escaping () -> Void)
+    @preconcurrency
+    func execute(qos: DispatchQoS, _ task: @escaping @Sendable () -> Void)

    /// Schedule a `task` that is executed by this `NIOTSEventLoop` after the given amount of time at the
    /// given `qos`.
-    func scheduleTask<T>(in time: TimeAmount, qos: DispatchQoS, _ task: @escaping () throws -> T) -> Scheduled<T>
+    @preconcurrency
+    func scheduleTask<T>(
+        in time: TimeAmount,
+        qos: DispatchQoS,
+        _ task: @escaping @Sendable () throws -> T
+    ) -> Scheduled<T>
 }

 /// The lifecycle state of a given event loop.
@ -49,8 +59,9 @@ private enum LifecycleState {
    case closed
 }

+// It's okay for NIOTSEventLoop to be unchecked Sendable, since the state is isolated to the EL.
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-internal class NIOTSEventLoop: QoSEventLoop {
+internal final class NIOTSEventLoop: QoSEventLoop, @unchecked Sendable {
    private let loop: DispatchQueue
    private let taskQueue: DispatchQueue
    private let inQueueKey: DispatchSpecificKey<UUID>
@ -114,23 +125,27 @@ internal class NIOTSEventLoop: QoSEventLoop {
        loop.setSpecific(key: inQueueKey, value: self.loopID)
    }

-    public func execute(_ task: @escaping () -> Void) {
+    @preconcurrency
+    public func execute(_ task: @escaping @Sendable () -> Void) {
        self.execute(qos: self.defaultQoS, task)
    }

-    public func execute(qos: DispatchQoS, _ task: @escaping () -> Void) {
+    @preconcurrency
+    public func execute(qos: DispatchQoS, _ task: @escaping @Sendable () -> Void) {
        // Ideally we'd not accept new work while closed. Sadly, that's not possible with the current APIs for this.
        self.taskQueue.async(qos: qos, execute: task)
    }

-    public func scheduleTask<T>(deadline: NIODeadline, _ task: @escaping () throws -> T) -> Scheduled<T> {
+    @preconcurrency
+    public func scheduleTask<T>(deadline: NIODeadline, _ task: @escaping @Sendable () throws -> T) -> Scheduled<T> {
        self.scheduleTask(deadline: deadline, qos: self.defaultQoS, task)
    }

+    @preconcurrency
    public func scheduleTask<T>(
        deadline: NIODeadline,
        qos: DispatchQoS,
-        _ task: @escaping () throws -> T
+        _ task: @escaping @Sendable () throws -> T
    ) -> Scheduled<T> {
        let p: EventLoopPromise<T> = self.makePromise()

@ -143,11 +158,12 @@ internal class NIOTSEventLoop: QoSEventLoop {
                p.fail(EventLoopError.shutdown)
                return
            }
-            do {
-                p.succeed(try task())
-            } catch {
-                p.fail(error)
+
+            p.assumeIsolated().completeWith(
+                Result {
+                    try task()
                }
+            )
        }
        timerSource.resume()

@ -165,16 +181,25 @@ internal class NIOTSEventLoop: QoSEventLoop {
        )
    }

-    public func scheduleTask<T>(in time: TimeAmount, _ task: @escaping () throws -> T) -> Scheduled<T> {
+    @preconcurrency
+    public func scheduleTask<T>(
+        in time: TimeAmount,
+        _ task: @escaping @Sendable () throws -> T
+    ) -> Scheduled<T> {
        self.scheduleTask(in: time, qos: self.defaultQoS, task)
    }

-    public func scheduleTask<T>(in time: TimeAmount, qos: DispatchQoS, _ task: @escaping () throws -> T) -> Scheduled<T>
-    {
+    @preconcurrency
+    public func scheduleTask<T>(
+        in time: TimeAmount,
+        qos: DispatchQoS,
+        _ task: @escaping @Sendable () throws -> T
+    ) -> Scheduled<T> {
        self.scheduleTask(deadline: NIODeadline.now() + time, qos: qos, task)
    }

-    public func shutdownGracefully(queue: DispatchQueue, _ callback: @escaping (Error?) -> Void) {
+    @preconcurrency
+    public func shutdownGracefully(queue: DispatchQueue, _ callback: @escaping @Sendable (Error?) -> Void) {
        guard self.canBeShutDownIndividually else {
            // The loops cannot be shut down by individually. They need to be shut down as a group and
            // `NIOTSEventLoopGroup` calls `closeGently` not this method.
--- a/Sources/NIOTransportServices/NIOTSEventLoopGroup.swift
+++ b/Sources/NIOTransportServices/NIOTSEventLoopGroup.swift
@ -82,7 +82,8 @@ public final class NIOTSEventLoopGroup: EventLoopGroup {
    }

    /// Shuts down all of the event loops, rendering them unable to perform further work.
-    public func shutdownGracefully(queue: DispatchQueue, _ callback: @escaping (Error?) -> Void) {
+    @preconcurrency
+    public func shutdownGracefully(queue: DispatchQueue, _ callback: @escaping @Sendable (Error?) -> Void) {
        guard self.canBeShutDown else {
            queue.async {
                callback(EventLoopError.unsupportedOperation)
@ -91,19 +92,19 @@ public final class NIOTSEventLoopGroup: EventLoopGroup {
        }
        let g = DispatchGroup()
        let q = DispatchQueue(label: "nio.transportservices.shutdowngracefullyqueue", target: queue)
-        var error: Error? = nil
+        let error: NIOLockedValueBox<Error?> = .init(nil)

        for loop in self.eventLoops {
            g.enter()
            loop.closeGently().recover { err in
-                q.sync { error = err }
+                q.sync { error.withLockedValue({ $0 = err }) }
            }.whenComplete { (_: Result<Void, Error>) in
                g.leave()
            }
        }

        g.notify(queue: q) {
-            callback(error)
+            callback(error.withLockedValue({ $0 }))
        }
    }

@ -145,4 +146,7 @@ public struct NIOTSClientTLSProvider: NIOClientTLSProvider {
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
 extension NIOTSEventLoopGroup: @unchecked Sendable {}

+@available(*, unavailable)
+extension NIOTSClientTLSProvider: Sendable {}
+
 #endif
--- a/Sources/NIOTransportServices/NIOTSListenerBootstrap.swift
+++ b/Sources/NIOTransportServices/NIOTSListenerBootstrap.swift
@ -17,7 +17,7 @@ import NIOCore
 import Dispatch
 import Network

-/// A ``NIOTSListenerBootstrap`` is an easy way to bootstrap a `NIOTSListenerChannel` when creating network servers.
+/// A ``NIOTSListenerBootstrap`` is an easy way to bootstrap a listener channel when creating network servers.
 ///
 /// Example:
 ///
@ -46,26 +46,29 @@ import Network
 ///     try! channel.closeFuture.wait() // wait forever as we never close the Channel
 /// ```
 ///
-/// The `EventLoopFuture` returned by `bind` will fire with a `NIOTSListenerChannel`. This is the channel that owns the
-/// listening socket. Each time it accepts a new connection it will fire a `NIOTSConnectionChannel` through the
-/// `ChannelPipeline` via `fireChannelRead`: as a result, the `NIOTSListenerChannel` operates on `Channel`s as inbound
-/// messages. Outbound messages are not supported on a `NIOTSListenerChannel` which means that each write attempt will
-/// fail.
+/// The `EventLoopFuture` returned by `bind` will fire with a channel. This is the channel that owns the listening socket. Each
+/// time it accepts a new connection it will fire a new child channel for the new connection through the `ChannelPipeline` via
+/// `fireChannelRead`: as a result, the listening channel operates on `Channel`s as inbound messages. Outbound messages are
+/// not supported on these listening channels, which means that each write attempt will fail.
 ///
-/// Accepted `NIOTSConnectionChannel`s operate on `ByteBuffer` as inbound data, and `IOData` as outbound data.
+/// Accepted channels operate on `ByteBuffer` as inbound data, and `IOData` as outbound data.
@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
 public final class NIOTSListenerBootstrap {
    private let group: EventLoopGroup
    private let childGroup: EventLoopGroup
-    private var serverChannelInit: ((Channel) -> EventLoopFuture<Void>)?
-    private var childChannelInit: ((Channel) -> EventLoopFuture<Void>)?
+    private var serverChannelInit: (@Sendable (Channel) -> EventLoopFuture<Void>)?
+    private var childChannelInit: (@Sendable (Channel) -> EventLoopFuture<Void>)?
    private var serverChannelOptions = ChannelOptions.Storage()
    private var childChannelOptions = ChannelOptions.Storage()
    private var serverQoS: DispatchQoS?
    private var childQoS: DispatchQoS?
    private var tcpOptions: NWProtocolTCP.Options = .init()
+    private var childTCPOptions: NWProtocolTCP.Options = .init()
    private var tlsOptions: NWProtocolTLS.Options?
+    private var childTLSOptions: NWProtocolTLS.Options?
    private var bindTimeout: TimeAmount?
+    private var nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
+    private var childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?

    /// Create a ``NIOTSListenerBootstrap`` for the `EventLoopGroup` `group`.
    ///
@ -78,7 +81,7 @@ public final class NIOTSListenerBootstrap {
    /// > Note: The "real" solution is described in https://github.com/apple/swift-nio/issues/674.
    ///
    /// - parameters:
-    ///     - group: The `EventLoopGroup` to use for the `NIOTSListenerChannel`.
+    ///     - group: The `EventLoopGroup` to use for the listening channel.
    public convenience init(group: EventLoopGroup) {
        self.init(group: group, childGroup: group)
    }
@ -86,7 +89,7 @@ public final class NIOTSListenerBootstrap {
    /// Create a ``NIOTSListenerBootstrap`` for the ``NIOTSEventLoopGroup`` `group`.
    ///
    /// - parameters:
-    ///     - group: The ``NIOTSEventLoopGroup`` to use for the `NIOTSListenerChannel`.
+    ///     - group: The ``NIOTSEventLoopGroup`` to use for the listening channel.
    public convenience init(group: NIOTSEventLoopGroup) {
        self.init(group: group as EventLoopGroup)
    }
@ -102,9 +105,9 @@ public final class NIOTSListenerBootstrap {
    /// > Note: The "real" solution is described in https://github.com/apple/swift-nio/issues/674.
    ///
    /// - parameters:
-    ///     - group: The `EventLoopGroup` to use for the `bind` of the `NIOTSListenerChannel`
-    ///         and to accept new `NIOTSConnectionChannel`s with.
-    ///     - childGroup: The `EventLoopGroup` to run the accepted `NIOTSConnectionChannel`s on.
+    ///     - group: The `EventLoopGroup` to use for the `bind` of the listening channel
+    ///         and to accept new child channels with.
+    ///     - childGroup: The `EventLoopGroup` to run the accepted child channels on.
    public convenience init(group: EventLoopGroup, childGroup: EventLoopGroup) {
        guard NIOTSBootstraps.isCompatible(group: group) && NIOTSBootstraps.isCompatible(group: childGroup) else {
            preconditionFailure(
@ -121,9 +124,9 @@ public final class NIOTSListenerBootstrap {
    /// validating that the `EventLoopGroup`s are compatible with ``NIOTSListenerBootstrap``.
    ///
    /// - parameters:
-    ///     - group: The `EventLoopGroup` to use for the `bind` of the `NIOTSListenerChannel`
-    ///         and to accept new `NIOTSConnectionChannel`s with.
-    ///     - childGroup: The `EventLoopGroup` to run the accepted `NIOTSConnectionChannel`s on.
+    ///     - group: The `EventLoopGroup` to use for the `bind` of the listening channel
+    ///         and to accept new child channels with.
+    ///     - childGroup: The `EventLoopGroup` to run the accepted child channels on.
    public init?(validatingGroup group: EventLoopGroup, childGroup: EventLoopGroup? = nil) {
        let childGroup = childGroup ?? group
        guard NIOTSBootstraps.isCompatible(group: group) && NIOTSBootstraps.isCompatible(group: childGroup) else {
@ -140,29 +143,31 @@ public final class NIOTSListenerBootstrap {
    /// Create a ``NIOTSListenerBootstrap``.
    ///
    /// - parameters:
-    ///     - group: The ``NIOTSEventLoopGroup`` to use for the `bind` of the `NIOTSListenerChannel`
-    ///         and to accept new `NIOTSConnectionChannel`s with.
-    ///     - childGroup: The ``NIOTSEventLoopGroup`` to run the accepted `NIOTSConnectionChannel`s on.
+    ///     - group: The ``NIOTSEventLoopGroup`` to use for the `bind` of the listening channel
+    ///         and to accept new child channels with.
+    ///     - childGroup: The ``NIOTSEventLoopGroup`` to run the accepted child channels on.
    public convenience init(group: NIOTSEventLoopGroup, childGroup: NIOTSEventLoopGroup) {
        self.init(group: group as EventLoopGroup, childGroup: childGroup as EventLoopGroup)
    }

-    /// Initialize the `NIOTSListenerChannel` with `initializer`. The most common task in initializer is to add
+    /// Initialize the listening channel with `initializer`. The most common task in initializer is to add
    /// `ChannelHandler`s to the `ChannelPipeline`.
    ///
-    /// The `NIOTSListenerChannel` uses the accepted `NIOTSConnectionChannel`s as inbound messages.
+    /// The listening channel uses the accepted child channels as inbound messages.
    ///
-    /// > Note: To set the initializer for the accepted `NIOTSConnectionChannel`s, look at
+    /// > Note: To set the initializer for the accepted child channels, look at
    ///     ``childChannelInitializer(_:)``.
    ///
    /// - parameters:
    ///     - initializer: A closure that initializes the provided `Channel`.
-    public func serverChannelInitializer(_ initializer: @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
+    @preconcurrency
+    public func serverChannelInitializer(_ initializer: @escaping @Sendable (Channel) -> EventLoopFuture<Void>) -> Self
+    {
        self.serverChannelInit = initializer
        return self
    }

-    /// Initialize the accepted `NIOTSConnectionChannel`s with `initializer`. The most common task in initializer is to add
+    /// Initialize the accepted child channels with `initializer`. The most common task in initializer is to add
    /// `ChannelHandler`s to the `ChannelPipeline`. Note that if the `initializer` fails then the error will be
    /// fired in the *parent* channel.
    ///
@ -170,14 +175,15 @@ public final class NIOTSListenerBootstrap {
    ///
    /// - parameters:
    ///     - initializer: A closure that initializes the provided `Channel`.
-    public func childChannelInitializer(_ initializer: @escaping (Channel) -> EventLoopFuture<Void>) -> Self {
+    @preconcurrency
+    public func childChannelInitializer(_ initializer: @escaping @Sendable (Channel) -> EventLoopFuture<Void>) -> Self {
        self.childChannelInit = initializer
        return self
    }

-    /// Specifies a `ChannelOption` to be applied to the `NIOTSListenerChannel`.
+    /// Specifies a `ChannelOption` to be applied to the listening channel.
    ///
-    /// > Note: To specify options for the accepted `NIOTSConnectionChannel`s, look at ``childChannelOption(_:value:)``.
+    /// > Note: To specify options for the accepted child channels, look at ``childChannelOption(_:value:)``.
    ///
    /// - parameters:
    ///     - option: The option to be applied.
@ -187,7 +193,7 @@ public final class NIOTSListenerBootstrap {
        return self
    }

-    /// Specifies a `ChannelOption` to be applied to the accepted `NIOTSConnectionChannel`s.
+    /// Specifies a `ChannelOption` to be applied to the accepted child channels.
    ///
    /// - parameters:
    ///     - option: The option to be applied.
@ -224,18 +230,46 @@ public final class NIOTSListenerBootstrap {
        return self
    }

-    /// Specifies the TCP options to use on the child `Channel`s.
+    /// Specifies the TCP options to use on the listener.
    public func tcpOptions(_ options: NWProtocolTCP.Options) -> Self {
        self.tcpOptions = options
        return self
    }

-    /// Specifies the TLS options to use on the child `Channel`s.
+    /// Specifies the TCP options to use on the child `Channel`s.
+    public func childTCPOptions(_ options: NWProtocolTCP.Options) -> Self {
+        self.childTCPOptions = options
+        return self
+    }
+
+    /// Specifies the TLS options to use on the listener.
    public func tlsOptions(_ options: NWProtocolTLS.Options) -> Self {
        self.tlsOptions = options
        return self
    }

+    /// Specifies the TLS options to use on the child `Channel`s.
+    public func childTLSOptions(_ options: NWProtocolTLS.Options) -> Self {
+        self.childTLSOptions = options
+        return self
+    }
+
+    /// Customise the `NWParameters` to be used when creating the `NWConnection` for the listener.
+    public func configureNWParameters(
+        _ configurator: @Sendable @escaping (NWParameters) -> Void
+    ) -> Self {
+        self.nwParametersConfigurator = configurator
+        return self
+    }
+
+    /// Customise the `NWParameters` to be used when creating the `NWConnection`s for the child `Channel`s.
+    public func configureChildNWParameters(
+        _ configurator: @Sendable @escaping (NWParameters) -> Void
+    ) -> Self {
+        self.childNWParametersConfigurator = configurator
+        return self
+    }
+
    /// Specifies a type of Multipath service to use for this listener, instead of the default
    /// service type for the event loop.
    ///
@ -246,7 +280,7 @@ public final class NIOTSListenerBootstrap {
        self.serverChannelOption(NIOTSChannelOptions.multipathServiceType, value: type)
    }

-    /// Bind the `NIOTSListenerChannel` to `host` and `port`.
+    /// Bind the listening channel to `host` and `port`.
    ///
    /// - parameters:
    ///     - host: The host to bind on.
@ -270,7 +304,7 @@ public final class NIOTSListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to `address`.
+    /// Bind the listening channel to `address`.
    ///
    /// - parameters:
    ///     - address: The `SocketAddress` to bind on.
@ -280,7 +314,7 @@ public final class NIOTSListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to a UNIX Domain Socket.
+    /// Bind the listening channel to a UNIX Domain Socket.
    ///
    /// - parameters:
    ///     - unixDomainSocketPath: The _Unix domain socket_ path to bind to. `unixDomainSocketPath` must not exist, it will be created by the system.
@ -295,7 +329,7 @@ public final class NIOTSListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to a given `NWEndpoint`.
+    /// Bind the listening channel to a given `NWEndpoint`.
    ///
    /// - parameters:
    ///     - endpoint: The `NWEndpoint` to bind this channel to.
@ -305,7 +339,7 @@ public final class NIOTSListenerBootstrap {
        }
    }

-    /// Bind the `NIOTSListenerChannel` to an existing `NWListener`.
+    /// Bind the listening channel to an existing `NWListener`.
    ///
    /// - parameters:
    ///     - listener: The NWListener to wrap.
@ -318,10 +352,10 @@ public final class NIOTSListenerBootstrap {
    private func bind0(
        existingNWListener: NWListener? = nil,
        shouldRegister: Bool,
-        _ binder: @escaping (NIOTSListenerChannel, EventLoopPromise<Void>) -> Void
+        _ binder: @escaping @Sendable (NIOTSListenerChannel, EventLoopPromise<Void>) -> Void
    ) -> EventLoopFuture<Channel> {
        let eventLoop = self.group.next() as! NIOTSEventLoop
-        let serverChannelInit = self.serverChannelInit ?? { _ in eventLoop.makeSucceededFuture(()) }
+        let serverChannelInit = self.serverChannelInit ?? { @Sendable _ in eventLoop.makeSucceededFuture(()) }
        let childChannelInit = self.childChannelInit
        let serverChannelOptions = self.serverChannelOptions
        let childChannelOptions = self.childChannelOptions
@ -334,10 +368,12 @@ public final class NIOTSListenerBootstrap {
                qos: self.serverQoS,
                tcpOptions: self.tcpOptions,
                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator,
                childLoopGroup: self.childGroup,
                childChannelQoS: self.childQoS,
-                childTCPOptions: self.tcpOptions,
-                childTLSOptions: self.tlsOptions
+                childTCPOptions: self.childTCPOptions,
+                childTLSOptions: self.childTLSOptions,
+                childNWParametersConfigurator: self.childNWParametersConfigurator
            )
        } else {
            serverChannel = NIOTSListenerChannel(
@ -345,24 +381,28 @@ public final class NIOTSListenerBootstrap {
                qos: self.serverQoS,
                tcpOptions: self.tcpOptions,
                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator,
                childLoopGroup: self.childGroup,
                childChannelQoS: self.childQoS,
-                childTCPOptions: self.tcpOptions,
-                childTLSOptions: self.tlsOptions
+                childTCPOptions: self.childTCPOptions,
+                childTLSOptions: self.childTLSOptions,
+                childNWParametersConfigurator: self.childNWParametersConfigurator
            )
        }

-        return eventLoop.submit {
+        return eventLoop.submit { [bindTimeout] in
            serverChannelOptions.applyAllChannelOptions(to: serverChannel).flatMap {
                serverChannelInit(serverChannel)
            }.flatMap {
                eventLoop.assertInEventLoop()
-                return serverChannel.pipeline.addHandler(
+                return eventLoop.makeCompletedFuture {
+                    try serverChannel.pipeline.syncOperations.addHandler(
                        AcceptHandler<NIOTSConnectionChannel>(
                            childChannelInitializer: childChannelInit,
                            childChannelOptions: childChannelOptions
                        )
                    )
+                }
            }.flatMap {
                if shouldRegister {
                    return serverChannel.register()
@ -373,7 +413,7 @@ public final class NIOTSListenerBootstrap {
                let bindPromise = eventLoop.makePromise(of: Void.self)
                binder(serverChannel, bindPromise)

-                if let bindTimeout = self.bindTimeout {
+                if let bindTimeout = bindTimeout {
                    let cancelTask = eventLoop.scheduleTask(in: bindTimeout) {
                        bindPromise.fail(NIOTSErrors.BindTimeout(timeout: bindTimeout))
                        serverChannel.close(promise: nil)
@ -400,7 +440,7 @@ public final class NIOTSListenerBootstrap {

@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
 extension NIOTSListenerBootstrap {
-    /// Bind the `NIOTSListenerChannel` to `host` and `port`.
+    /// Bind the listening channel to `host` and `port`.
    ///
    /// - Parameters:
    ///   - host: The host to bind on.
@ -445,7 +485,7 @@ extension NIOTSListenerBootstrap {
        ).get()
    }

-    /// Bind the `NIOTSListenerChannel` to `address`.
+    /// Bind the listening channel to `address`.
    ///
    /// - Parameters:
    ///   - address: The `SocketAddress` to bind on.
@ -475,7 +515,7 @@ extension NIOTSListenerBootstrap {
        ).get()
    }

-    /// Bind the `NIOTSListenerChannel` to a given `NWEndpoint`.
+    /// Bind the listening channel to a given `NWEndpoint`.
    ///
    /// - Parameters:
    ///   - endpoint: The `NWEndpoint` to bind this channel to.
@ -508,7 +548,7 @@ extension NIOTSListenerBootstrap {
        ).get()
    }

-    /// Bind the `NIOTSListenerChannel` to an existing `NWListener`.
+    /// Bind the listening channel to an existing `NWListener`.
    ///
    /// - Parameters:
    ///   - listener: The NWListener to wrap.
@ -537,7 +577,7 @@ extension NIOTSListenerBootstrap {
        existingNWListener: NWListener? = nil,
        serverBackPressureStrategy: NIOAsyncSequenceProducerBackPressureStrategies.HighLowWatermark?,
        childChannelInitializer: @escaping @Sendable (Channel) -> EventLoopFuture<ChannelInitializerResult>,
-        registration: @escaping (NIOTSListenerChannel, EventLoopPromise<Void>) -> Void
+        registration: @escaping @Sendable (NIOTSListenerChannel, EventLoopPromise<Void>) -> Void
    ) -> EventLoopFuture<NIOAsyncChannel<ChannelInitializerResult, Never>> {
        let eventLoop = self.group.next() as! NIOTSEventLoop
        let serverChannelInit = self.serverChannelInit ?? { _ in eventLoop.makeSucceededFuture(()) }
@ -553,10 +593,12 @@ extension NIOTSListenerBootstrap {
                qos: self.serverQoS,
                tcpOptions: self.tcpOptions,
                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator,
                childLoopGroup: self.childGroup,
                childChannelQoS: self.childQoS,
                childTCPOptions: self.tcpOptions,
-                childTLSOptions: self.tlsOptions
+                childTLSOptions: self.tlsOptions,
+                childNWParametersConfigurator: self.nwParametersConfigurator
            )
        } else {
            serverChannel = NIOTSListenerChannel(
@ -564,14 +606,16 @@ extension NIOTSListenerBootstrap {
                qos: self.serverQoS,
                tcpOptions: self.tcpOptions,
                tlsOptions: self.tlsOptions,
+                nwParametersConfigurator: self.nwParametersConfigurator,
                childLoopGroup: self.childGroup,
                childChannelQoS: self.childQoS,
                childTCPOptions: self.tcpOptions,
-                childTLSOptions: self.tlsOptions
+                childTLSOptions: self.tlsOptions,
+                childNWParametersConfigurator: self.nwParametersConfigurator
            )
        }

-        return eventLoop.submit {
+        return eventLoop.submit { [bindTimeout] in
            serverChannelOptions.applyAllChannelOptions(to: serverChannel).flatMap {
                serverChannelInit(serverChannel)
            }.flatMap { (_) -> EventLoopFuture<NIOAsyncChannel<ChannelInitializerResult, Never>> in
@ -585,7 +629,7 @@ extension NIOTSListenerBootstrap {
                    )
                    let asyncChannel = try NIOAsyncChannel<ChannelInitializerResult, Never>
                        ._wrapAsyncChannelWithTransformations(
-                            synchronouslyWrapping: serverChannel,
+                            wrappingChannelSynchronously: serverChannel,
                            backPressureStrategy: serverBackPressureStrategy,
                            channelReadTransformation: { channel -> EventLoopFuture<(ChannelInitializerResult)> in
                                // The channelReadTransformation is run on the EL of the server channel
@ -600,7 +644,7 @@ extension NIOTSListenerBootstrap {
                    let bindPromise = eventLoop.makePromise(of: Void.self)
                    registration(serverChannel, bindPromise)

-                    if let bindTimeout = self.bindTimeout {
+                    if let bindTimeout = bindTimeout {
                        let cancelTask = eventLoop.scheduleTask(in: bindTimeout) {
                            bindPromise.fail(NIOTSErrors.BindTimeout(timeout: bindTimeout))
                            serverChannel.close(promise: nil)
@ -627,4 +671,6 @@ extension NIOTSListenerBootstrap {
    }
 }

+@available(*, unavailable)
+extension NIOTSListenerBootstrap: Sendable {}
 #endif
--- a/Sources/NIOTransportServices/NIOTSListenerChannel.swift
+++ b/Sources/NIOTransportServices/NIOTSListenerChannel.swift
@ -81,19 +81,23 @@ internal final class NIOTSListenerChannel: StateManagedListenerChannel<NIOTSConn
        qos: DispatchQoS? = nil,
        tcpOptions: NWProtocolTCP.Options,
        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?,
        childLoopGroup: EventLoopGroup,
        childChannelQoS: DispatchQoS?,
        childTCPOptions: NWProtocolTCP.Options,
-        childTLSOptions: NWProtocolTLS.Options?
+        childTLSOptions: NWProtocolTLS.Options?,
+        childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.init(
            eventLoop: eventLoop,
            protocolOptions: .tcp(tcpOptions),
            tlsOptions: tlsOptions,
+            nwParametersConfigurator: nwParametersConfigurator,
            childLoopGroup: childLoopGroup,
            childChannelQoS: childChannelQoS,
            childProtocolOptions: .tcp(childTCPOptions),
-            childTLSOptions: childTLSOptions
+            childTLSOptions: childTLSOptions,
+            childNWParametersConfigurator: childNWParametersConfigurator
        )
    }

@ -104,10 +108,12 @@ internal final class NIOTSListenerChannel: StateManagedListenerChannel<NIOTSConn
        qos: DispatchQoS? = nil,
        tcpOptions: NWProtocolTCP.Options,
        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?,
        childLoopGroup: EventLoopGroup,
        childChannelQoS: DispatchQoS?,
        childTCPOptions: NWProtocolTCP.Options,
-        childTLSOptions: NWProtocolTLS.Options?
+        childTLSOptions: NWProtocolTLS.Options?,
+        childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.init(
            wrapping: listener,
@ -115,10 +121,12 @@ internal final class NIOTSListenerChannel: StateManagedListenerChannel<NIOTSConn
            qos: qos,
            protocolOptions: .tcp(tcpOptions),
            tlsOptions: tlsOptions,
+            nwParametersConfigurator: nwParametersConfigurator,
            childLoopGroup: childLoopGroup,
            childChannelQoS: childChannelQoS,
            childProtocolOptions: .tcp(childTCPOptions),
-            childTLSOptions: childTLSOptions
+            childTLSOptions: childTLSOptions,
+            childNWParametersConfigurator: childNWParametersConfigurator
        )
    }

@ -134,10 +142,11 @@ internal final class NIOTSListenerChannel: StateManagedListenerChannel<NIOTSConn
            parent: self,
            qos: self.childChannelQoS,
            tcpOptions: self.childTCPOptions,
-            tlsOptions: self.childTLSOptions
+            tlsOptions: self.childTLSOptions,
+            nwParametersConfigurator: self.childNWParametersConfigurator
        )

-        self.pipeline.fireChannelRead(NIOAny(newChannel))
+        self.pipeline.fireChannelRead(newChannel)
        self.pipeline.fireChannelReadComplete()
    }

--- a/Sources/NIOTransportServices/NIOTSNetworkEvents.swift
+++ b/Sources/NIOTransportServices/NIOTSNetworkEvents.swift
@ -13,7 +13,7 @@
 //===----------------------------------------------------------------------===//

 #if canImport(Network)
-@preconcurrency import Network
+import Network
 import NIOCore

 /// A tag protocol that can be used to cover all network events emitted by `NIOTransportServices`.
@ -23,7 +23,7 @@ import NIOCore
 public protocol NIOTSNetworkEvent: Equatable, _NIOPreconcurrencySendable {}

@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
-public enum NIOTSNetworkEvents {
+public enum NIOTSNetworkEvents: Sendable {
    /// ``BetterPathAvailable`` is fired whenever the OS has informed NIO that there is a better
    /// path available to the endpoint that this `Channel` is currently connected to,
    /// e.g. the current connection is using an expensive cellular connection and
--- a/Sources/NIOTransportServices/StateManagedListenerChannel.swift
+++ b/Sources/NIOTransportServices/StateManagedListenerChannel.swift
@ -67,6 +67,9 @@ internal class StateManagedListenerChannel<ChildChannel: StateManagedChannel>: S
    /// The TLS options for this listener.
    internal let tlsOptions: NWProtocolTLS.Options?

+    /// A customization point for this listener's `NWParameters`.
+    internal let nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?
+
    /// The `DispatchQueue` that socket events for this connection will be dispatched onto.
    internal let connectionQueue: DispatchQueue

@ -113,6 +116,9 @@ internal class StateManagedListenerChannel<ChildChannel: StateManagedChannel>: S
    /// The TLS options to use for child channels.
    internal let childTLSOptions: NWProtocolTLS.Options?

+    /// A customization point for each child's `NWParameters`.
+    internal let childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?
+
    /// The cache of the local and remote socket addresses. Must be accessed using _addressCacheLock.
    internal var addressCache = AddressCache(local: nil, remote: nil)

@ -130,20 +136,24 @@ internal class StateManagedListenerChannel<ChildChannel: StateManagedChannel>: S
        qos: DispatchQoS? = nil,
        protocolOptions: ProtocolOptions,
        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?,
        childLoopGroup: EventLoopGroup,
        childChannelQoS: DispatchQoS?,
        childProtocolOptions: ProtocolOptions,
-        childTLSOptions: NWProtocolTLS.Options?
+        childTLSOptions: NWProtocolTLS.Options?,
+        childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.tsEventLoop = eventLoop
        self.closePromise = eventLoop.makePromise()
        self.connectionQueue = eventLoop.channelQueue(label: "nio.transportservices.listenerchannel", qos: qos)
        self.protocolOptions = protocolOptions
        self.tlsOptions = tlsOptions
+        self.nwParametersConfigurator = nwParametersConfigurator
        self.childLoopGroup = childLoopGroup
        self.childChannelQoS = childChannelQoS
        self.childProtocolOptions = childProtocolOptions
        self.childTLSOptions = childTLSOptions
+        self.childNWParametersConfigurator = childNWParametersConfigurator

        // Must come last, as it requires self to be completely initialized.
        self._pipeline = ChannelPipeline(channel: self)
@ -155,20 +165,24 @@ internal class StateManagedListenerChannel<ChildChannel: StateManagedChannel>: S
        qos: DispatchQoS? = nil,
        protocolOptions: ProtocolOptions,
        tlsOptions: NWProtocolTLS.Options?,
+        nwParametersConfigurator: (@Sendable (NWParameters) -> Void)?,
        childLoopGroup: EventLoopGroup,
        childChannelQoS: DispatchQoS?,
        childProtocolOptions: ProtocolOptions,
-        childTLSOptions: NWProtocolTLS.Options?
+        childTLSOptions: NWProtocolTLS.Options?,
+        childNWParametersConfigurator: (@Sendable (NWParameters) -> Void)?
    ) {
        self.init(
            eventLoop: eventLoop,
            qos: qos,
            protocolOptions: protocolOptions,
            tlsOptions: tlsOptions,
+            nwParametersConfigurator: nwParametersConfigurator,
            childLoopGroup: childLoopGroup,
            childChannelQoS: childChannelQoS,
            childProtocolOptions: childProtocolOptions,
-            childTLSOptions: childTLSOptions
+            childTLSOptions: childTLSOptions,
+            childNWParametersConfigurator: childNWParametersConfigurator
        )
        self.nwListener = listener
    }
@ -398,6 +412,8 @@ extension StateManagedListenerChannel {

        parameters.multipathServiceType = self.multipathServiceType

+        self.nwParametersConfigurator?(parameters)
+
        let listener: NWListener
        do {
            listener = try NWListener(using: parameters)
@ -533,4 +549,9 @@ extension StateManagedListenerChannel {
    }
 }

+// We inherit from StateManagedListenerChannel in NIOTSDatagramListenerChannel, so we can't mark
+// it as Sendable safely.
+@available(OSX 10.14, iOS 12.0, tvOS 12.0, watchOS 6.0, *)
+extension StateManagedListenerChannel: @unchecked Sendable {}
+
 #endif
--- a/Sources/NIOTransportServices/StateManagedNWConnectionChannel.swift
+++ b/Sources/NIOTransportServices/StateManagedNWConnectionChannel.swift
@ -83,6 +83,8 @@ internal protocol StateManagedNWConnectionChannel: StateManagedChannel where Act

    var multipathServiceType: NWParameters.MultipathServiceType { get }

+    var nwParametersConfigurator: (@Sendable (NWParameters) -> Void)? { get }
+
    func setChannelSpecificOption0<Option: ChannelOption>(option: Option, value: Option.Value) throws

    func getChannelSpecificOption0<Option: ChannelOption>(option: Option) throws -> Option.Value
@ -182,7 +184,7 @@ extension StateManagedNWConnectionChannel {
            preconditionFailure("nwconnection cannot be nil while channel is active")
        }

-        func completionCallback(promise: EventLoopPromise<Void>?, sentBytes: Int) -> ((NWError?) -> Void) {
+        func completionCallback(promise: EventLoopPromise<Void>?, sentBytes: Int) -> (@Sendable (NWError?) -> Void) {
            { error in
                if let error = error {
                    promise?.fail(error)
@ -242,6 +244,7 @@ extension StateManagedNWConnectionChannel {
        connection.betterPathUpdateHandler = self.betterPathHandler
        connection.viabilityUpdateHandler = self.viabilityUpdateHandler
        connection.pathUpdateHandler = self.pathChangedHandler(newPath:)
+        self.nwParametersConfigurator?(connection.parameters)
        connection.start(queue: self.connectionQueue)
    }

@ -314,7 +317,7 @@ extension StateManagedNWConnectionChannel {
            return
        }

-        func completionCallback(for promise: EventLoopPromise<Void>?) -> ((NWError?) -> Void) {
+        func completionCallback(for promise: EventLoopPromise<Void>?) -> (@Sendable (NWError?) -> Void) {
            { error in
                if let error = error {
                    promise?.fail(error)
@ -432,7 +435,7 @@ extension StateManagedNWConnectionChannel {
            // APIs.
            var buffer = self.allocator.buffer(capacity: content.count)
            buffer.writeBytes(content)
-            self.pipeline.fireChannelRead(NIOAny(buffer))
+            self.pipeline.fireChannelRead(buffer)
            self.pipeline.fireChannelReadComplete()
        }

--- a/Tests/NIOTransportServicesTests/NIOFilterEmptyWritesHandlerTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOFilterEmptyWritesHandlerTests.swift
@ -42,7 +42,7 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
    func testEmptyWritePromise() {
        let emptyWrite = self.allocator.buffer(capacity: 0)
        let emptyWritePromise = self.eventLoop.makePromise(of: Void.self)
-        self.channel.write(NIOAny(emptyWrite), promise: emptyWritePromise)
+        self.channel.write(emptyWrite, promise: emptyWritePromise)
        self.channel.flush()
        XCTAssertNoThrow(
            try emptyWritePromise.futureResult.wait()
@ -53,7 +53,7 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
    }

    func testEmptyWritesNoWriteThrough() {
-        class OutboundTestHandler: ChannelOutboundHandler {
+        final class OutboundTestHandler: ChannelOutboundHandler, Sendable {
            typealias OutboundIn = ByteBuffer
            typealias OutboundOut = ByteBuffer

@ -75,9 +75,9 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
        let emptyWrite = self.allocator.buffer(capacity: 0)
        let thenEmptyWrite = self.allocator.buffer(capacity: 0)
        let thenEmptyWritePromise = self.eventLoop.makePromise(of: Void.self)
-        self.channel.write(NIOAny(emptyWrite), promise: nil)
+        self.channel.write(emptyWrite, promise: nil)
        self.channel.write(
-            NIOAny(thenEmptyWrite),
+            thenEmptyWrite,
            promise: thenEmptyWritePromise
        )
        self.channel.flush()
@ -98,20 +98,20 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
            case thenEmptyWrite
        }
        var checkOrder = CheckOrder.noWrite
-        someWritePromise.futureResult.whenSuccess {
+        someWritePromise.futureResult.assumeIsolated().whenSuccess {
            XCTAssertEqual(checkOrder, .noWrite)
            checkOrder = .someWrite
        }
-        thenEmptyWritePromise.futureResult.whenSuccess {
+        thenEmptyWritePromise.futureResult.assumeIsolated().whenSuccess {
            XCTAssertEqual(checkOrder, .someWrite)
            checkOrder = .thenEmptyWrite
        }
        self.channel.write(
-            NIOAny(someWrite),
+            someWrite,
            promise: someWritePromise
        )
        self.channel.write(
-            NIOAny(thenEmptyWrite),
+            thenEmptyWrite,
            promise: thenEmptyWritePromise
        )
        self.channel.flush()
@ -136,20 +136,20 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
            case thenEmptyWrite
        }
        var checkOrder = CheckOrder.noWrite
-        emptyWritePromise.futureResult.whenSuccess {
+        emptyWritePromise.futureResult.assumeIsolated().whenSuccess {
            XCTAssertEqual(checkOrder, .noWrite)
            checkOrder = .emptyWrite
        }
-        thenEmptyWritePromise.futureResult.whenSuccess {
+        thenEmptyWritePromise.futureResult.assumeIsolated().whenSuccess {
            XCTAssertEqual(checkOrder, .emptyWrite)
            checkOrder = .thenEmptyWrite
        }
        self.channel.write(
-            NIOAny(emptyWrite),
+            emptyWrite,
            promise: emptyWritePromise
        )
        self.channel.write(
-            NIOAny(thenEmptyWrite),
+            thenEmptyWrite,
            promise: thenEmptyWritePromise
        )
        self.channel.flush()
@ -174,21 +174,21 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
            case thenEmptyWrite
        }
        var checkOrder = CheckOrder.noWrite
-        emptyWritePromise.futureResult.whenSuccess {
+        emptyWritePromise.futureResult.assumeIsolated().whenSuccess {
            XCTAssertEqual(checkOrder, .noWrite)
            checkOrder = .emptyWrite
        }
-        thenSomeWritePromise.futureResult.whenSuccess {
+        thenSomeWritePromise.futureResult.assumeIsolated().whenSuccess {
            XCTAssertEqual(checkOrder, .emptyWrite)
            checkOrder = .thenSomeWrite
        }
-        thenEmptyWritePromise.futureResult.whenSuccess {
+        thenEmptyWritePromise.futureResult.assumeIsolated().whenSuccess {
            XCTAssertEqual(checkOrder, .thenSomeWrite)
            checkOrder = .thenEmptyWrite
        }
-        self.channel.write(NIOAny(emptyWrite), promise: emptyWritePromise)
-        self.channel.write(NIOAny(thenSomeWrite), promise: thenSomeWritePromise)
-        self.channel.write(NIOAny(thenEmptyWrite), promise: thenEmptyWritePromise)
+        self.channel.write(emptyWrite, promise: emptyWritePromise)
+        self.channel.write(thenSomeWrite, promise: thenSomeWritePromise)
+        self.channel.write(thenEmptyWrite, promise: thenEmptyWritePromise)
        self.channel.flush()
        XCTAssertNoThrow(try thenEmptyWritePromise.futureResult.wait())
        XCTAssertNoThrow(
@ -205,9 +205,9 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
        let thenEmptyWrite = self.allocator.buffer(capacity: 0)
        let thenSomeWrite = self.allocator.bufferFor(string: "then some")
        let thenSomeWritePromise = self.eventLoop.makePromise(of: Void.self)
-        self.channel.write(NIOAny(someWrite), promise: nil)
-        self.channel.write(NIOAny(thenEmptyWrite), promise: nil)
-        self.channel.write(NIOAny(thenSomeWrite), promise: thenSomeWritePromise)
+        self.channel.write(someWrite, promise: nil)
+        self.channel.write(thenEmptyWrite, promise: nil)
+        self.channel.write(thenSomeWrite, promise: thenSomeWritePromise)
        self.channel.flush()
        XCTAssertNoThrow(try thenSomeWritePromise.futureResult.wait())
        var someWriteOutput: ByteBuffer?
@ -228,7 +228,7 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
    func testSomeWriteAndFlushThenSomeWriteAndFlush() {
        let someWrite = self.allocator.bufferFor(string: "non empty")
        var someWritePromise: EventLoopPromise<Void>! = self.eventLoop.makePromise()
-        self.channel.write(NIOAny(someWrite), promise: someWritePromise)
+        self.channel.write(someWrite, promise: someWritePromise)
        self.channel.flush()
        XCTAssertNoThrow(
            try someWritePromise.futureResult.wait()
@ -239,7 +239,7 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
        someWritePromise = nil
        let thenSomeWrite = self.allocator.bufferFor(string: "then some")
        var thenSomeWritePromise: EventLoopPromise<Void>! = self.eventLoop.makePromise()
-        self.channel.write(NIOAny(thenSomeWrite), promise: thenSomeWritePromise)
+        self.channel.write(thenSomeWrite, promise: thenSomeWritePromise)
        self.channel.flush()
        XCTAssertNoThrow(
            try thenSomeWritePromise.futureResult.wait()
@ -253,7 +253,7 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
    func testEmptyWriteAndFlushThenEmptyWriteAndFlush() {
        let emptyWrite = self.allocator.buffer(capacity: 0)
        var emptyWritePromise: EventLoopPromise<Void>! = self.eventLoop.makePromise()
-        self.channel.write(NIOAny(emptyWrite), promise: emptyWritePromise)
+        self.channel.write(emptyWrite, promise: emptyWritePromise)
        self.channel.flush()
        XCTAssertNoThrow(
            try emptyWritePromise.futureResult.wait()
@ -264,7 +264,7 @@ class NIOFilterEmptyWritesHandlerTests: XCTestCase {
        emptyWritePromise = nil
        let thenEmptyWrite = self.allocator.buffer(capacity: 0)
        var thenEmptyWritePromise: EventLoopPromise<Void>! = self.eventLoop.makePromise()
-        self.channel.write(NIOAny(thenEmptyWrite), promise: thenEmptyWritePromise)
+        self.channel.write(thenEmptyWrite, promise: thenEmptyWritePromise)
        self.channel.flush()
        XCTAssertNoThrow(
            try thenEmptyWritePromise.futureResult.wait()
--- a/Tests/NIOTransportServicesTests/NIOTSAsyncBootstrapTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSAsyncBootstrapTests.swift
@ -85,12 +85,12 @@ private final class TLSUserEventHandler: ChannelInboundHandler, RemovableChannel
            let alpn = String(string.dropFirst(15))
            context.writeAndFlush(.init(ByteBuffer(string: "alpn:\(alpn)")), promise: nil)
            context.fireUserInboundEventTriggered(TLSUserEvent.handshakeCompleted(negotiatedProtocol: alpn))
-            context.pipeline.removeHandler(self, promise: nil)
+            context.pipeline.syncOperations.removeHandler(self, promise: nil)
        } else if string.hasPrefix("alpn:") {
            context.fireUserInboundEventTriggered(
                TLSUserEvent.handshakeCompleted(negotiatedProtocol: String(string.dropFirst(5)))
            )
-            context.pipeline.removeHandler(self, promise: nil)
+            context.pipeline.syncOperations.removeHandler(self, promise: nil)
        } else {
            context.fireChannelRead(data)
        }
@ -182,7 +182,9 @@ final class AsyncChannelBootstrapTests: XCTestCase {
    func testServerClientBootstrap_withAsyncChannel_andHostPort() async throws {
        let eventLoopGroup = NIOTSEventLoopGroup(loopCount: 3)
        defer {
-            try! eventLoopGroup.syncShutdownGracefully()
+            Task {
+                try! await eventLoopGroup.shutdownGracefully()
+            }
        }

        let channel = try await NIOTSListenerBootstrap(group: eventLoopGroup)
@ -240,7 +242,9 @@ final class AsyncChannelBootstrapTests: XCTestCase {
    func testAsyncChannelProtocolNegotiation() async throws {
        let eventLoopGroup = NIOTSEventLoopGroup(loopCount: 3)
        defer {
-            try! eventLoopGroup.syncShutdownGracefully()
+            Task {
+                try! await eventLoopGroup.shutdownGracefully()
+            }
        }

        let channel = try await NIOTSListenerBootstrap(group: eventLoopGroup)
@ -251,7 +255,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
                port: 0
            ) { channel in
                channel.eventLoop.makeCompletedFuture {
-                    try self.configureProtocolNegotiationHandlers(channel: channel).protocolNegotiationResult
+                    try Self.configureProtocolNegotiationHandlers(channel: channel).protocolNegotiationResult
                }
            }

@ -323,7 +327,9 @@ final class AsyncChannelBootstrapTests: XCTestCase {
    func testAsyncChannelNestedProtocolNegotiation() async throws {
        let eventLoopGroup = NIOTSEventLoopGroup(loopCount: 3)
        defer {
-            try! eventLoopGroup.syncShutdownGracefully()
+            Task {
+                try! await eventLoopGroup.shutdownGracefully()
+            }
        }

        let channel = try await NIOTSListenerBootstrap(group: eventLoopGroup)
@ -334,7 +340,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
                port: 0
            ) { channel in
                channel.eventLoop.makeCompletedFuture {
-                    try self.configureNestedProtocolNegotiationHandlers(channel: channel).protocolNegotiationResult
+                    try Self.configureNestedProtocolNegotiationHandlers(channel: channel).protocolNegotiationResult
                }
            }

@ -459,7 +465,9 @@ final class AsyncChannelBootstrapTests: XCTestCase {
        }
        let eventLoopGroup = NIOTSEventLoopGroup(loopCount: 3)
        defer {
-            try! eventLoopGroup.syncShutdownGracefully()
+            Task {
+                try! await eventLoopGroup.shutdownGracefully()
+            }
        }
        let channels = NIOLockedValueBox<[Channel]>([Channel]())

@ -478,7 +486,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
            port: 0
        ) { channel in
            channel.eventLoop.makeCompletedFuture {
-                try self.configureProtocolNegotiationHandlers(channel: channel).protocolNegotiationResult
+                try Self.configureProtocolNegotiationHandlers(channel: channel).protocolNegotiationResult
            }
        }

@ -585,7 +593,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
                to: .init(ipAddress: "127.0.0.1", port: port)
            ) { channel in
                channel.eventLoop.makeCompletedFuture {
-                    try self.configureProtocolNegotiationHandlers(channel: channel, proposedALPN: proposedALPN)
+                    try Self.configureProtocolNegotiationHandlers(channel: channel, proposedALPN: proposedALPN)
                        .protocolNegotiationResult
                }
            }
@ -602,7 +610,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
                to: .init(ipAddress: "127.0.0.1", port: port)
            ) { channel in
                channel.eventLoop.makeCompletedFuture {
-                    try self.configureNestedProtocolNegotiationHandlers(
+                    try Self.configureNestedProtocolNegotiationHandlers(
                        channel: channel,
                        proposedOuterALPN: proposedOuterALPN,
                        proposedInnerALPN: proposedInnerALPN
@ -612,18 +620,18 @@ final class AsyncChannelBootstrapTests: XCTestCase {
    }

    @discardableResult
-    private func configureProtocolNegotiationHandlers(
+    private static func configureProtocolNegotiationHandlers(
        channel: Channel,
        proposedALPN: TLSUserEventHandler.ALPN? = nil
    ) throws -> NIOTypedApplicationProtocolNegotiationHandler<NegotiationResult> {
        try channel.pipeline.syncOperations.addHandler(ByteToMessageHandler(LineDelimiterCoder()))
        try channel.pipeline.syncOperations.addHandler(MessageToByteHandler(LineDelimiterCoder()))
        try channel.pipeline.syncOperations.addHandler(TLSUserEventHandler(proposedALPN: proposedALPN))
-        return try self.addTypedApplicationProtocolNegotiationHandler(to: channel)
+        return try Self.addTypedApplicationProtocolNegotiationHandler(to: channel)
    }

    @discardableResult
-    private func configureNestedProtocolNegotiationHandlers(
+    private static func configureNestedProtocolNegotiationHandlers(
        channel: Channel,
        proposedOuterALPN: TLSUserEventHandler.ALPN? = nil,
        proposedInnerALPN: TLSUserEventHandler.ALPN? = nil
@ -642,7 +650,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
                        try channel.pipeline.syncOperations.addHandler(
                            TLSUserEventHandler(proposedALPN: proposedInnerALPN)
                        )
-                        let negotiationFuture = try self.addTypedApplicationProtocolNegotiationHandler(to: channel)
+                        let negotiationFuture = try Self.addTypedApplicationProtocolNegotiationHandler(to: channel)

                        return negotiationFuture.protocolNegotiationResult
                    }
@ -651,7 +659,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
                        try channel.pipeline.syncOperations.addHandler(
                            TLSUserEventHandler(proposedALPN: proposedInnerALPN)
                        )
-                        let negotiationHandler = try self.addTypedApplicationProtocolNegotiationHandler(to: channel)
+                        let negotiationHandler = try Self.addTypedApplicationProtocolNegotiationHandler(to: channel)

                        return negotiationHandler.protocolNegotiationResult
                    }
@ -667,7 +675,7 @@ final class AsyncChannelBootstrapTests: XCTestCase {
    }

    @discardableResult
-    private func addTypedApplicationProtocolNegotiationHandler(
+    private static func addTypedApplicationProtocolNegotiationHandler(
        to channel: Channel
    ) throws -> NIOTypedApplicationProtocolNegotiationHandler<NegotiationResult> {
        let negotiationHandler = NIOTypedApplicationProtocolNegotiationHandler<NegotiationResult> {
--- a/Tests/NIOTransportServicesTests/NIOTSBootstrapTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSBootstrapTests.swift
@ -24,58 +24,41 @@ import Foundation

@available(macOS 10.14, iOS 12.0, tvOS 12.0, watchOS 6, *)
 final class NIOTSBootstrapTests: XCTestCase {
-    var groupBag: [NIOTSEventLoopGroup]? = nil  // protected by `self.lock`
-    let lock = NIOLock()
-
-    override func setUp() {
-        self.lock.withLock {
-            XCTAssertNil(self.groupBag)
-            self.groupBag = []
-        }
-    }
-
-    override func tearDown() {
-        XCTAssertNoThrow(
-            try self.lock.withLock {
-                guard let groupBag = self.groupBag else {
-                    XCTFail()
-                    return
-                }
-                for group in groupBag {
+    func testBootstrapsTolerateFuturesFromDifferentEventLoopsReturnedInInitializers() throws {
+        let groupBag: NIOLockedValueBox<[NIOTSEventLoopGroup]> = .init([])
+        defer {
+            try! groupBag.withLockedValue {
+                for group in $0 {
                    XCTAssertNoThrow(try group.syncShutdownGracefully())
                }
-
-                self.groupBag = nil
            }
-        )
        }

-    func freshEventLoop() -> EventLoop {
+        @Sendable func freshEventLoop() -> EventLoop {
            let group: NIOTSEventLoopGroup = .init(loopCount: 1, defaultQoS: .default)
-        self.lock.withLock {
-            self.groupBag!.append(group)
+            groupBag.withLockedValue {
+                $0.append(group)
            }
            return group.next()
        }

-    func testBootstrapsTolerateFuturesFromDifferentEventLoopsReturnedInInitializers() throws {
-        let childChannelDone = self.freshEventLoop().makePromise(of: Void.self)
-        let serverChannelDone = self.freshEventLoop().makePromise(of: Void.self)
+        let childChannelDone = freshEventLoop().makePromise(of: Void.self)
+        let serverChannelDone = freshEventLoop().makePromise(of: Void.self)
        let serverChannel = try assertNoThrowWithValue(
-            NIOTSListenerBootstrap(group: self.freshEventLoop())
+            NIOTSListenerBootstrap(group: freshEventLoop())
                .childChannelInitializer { channel in
                    channel.eventLoop.preconditionInEventLoop()
                    defer {
                        childChannelDone.succeed(())
                    }
-                    return self.freshEventLoop().makeSucceededFuture(())
+                    return freshEventLoop().makeSucceededFuture(())
                }
                .serverChannelInitializer { channel in
                    channel.eventLoop.preconditionInEventLoop()
                    defer {
                        serverChannelDone.succeed(())
                    }
-                    return self.freshEventLoop().makeSucceededFuture(())
+                    return freshEventLoop().makeSucceededFuture(())
                }
                .bind(host: "127.0.0.1", port: 0)
                .wait()
@ -85,10 +68,10 @@ final class NIOTSBootstrapTests: XCTestCase {
        }

        let client = try assertNoThrowWithValue(
-            NIOTSConnectionBootstrap(group: self.freshEventLoop())
+            NIOTSConnectionBootstrap(group: freshEventLoop())
                .channelInitializer { channel in
                    channel.eventLoop.preconditionInEventLoop()
-                    return self.freshEventLoop().makeSucceededFuture(())
+                    return freshEventLoop().makeSucceededFuture(())
                }
                .connect(to: serverChannel.localAddress!)
                .wait()
@ -140,7 +123,9 @@ final class NIOTSBootstrapTests: XCTestCase {
            return try NIOTSListenerBootstrap(group: group)
                .childChannelInitializer { channel in
                    XCTAssertEqual(0, numberOfConnections.loadThenWrappingIncrement(ordering: .relaxed))
-                    return channel.pipeline.addHandler(TellMeIfConnectionIsTLSHandler(isTLS: isTLS))
+                    return channel.eventLoop.makeCompletedFuture {
+                        try channel.pipeline.syncOperations.addHandler(TellMeIfConnectionIsTLSHandler(isTLS: isTLS))
+                    }
                }
                .bind(host: "127.0.0.1", port: 0)
                .wait()
@ -175,8 +160,7 @@ final class NIOTSBootstrapTests: XCTestCase {
        )
        .enableTLS()

-        var buffer = server1.allocator.buffer(capacity: 2)
-        buffer.writeString("NO")
+        let buffer = server1.allocator.buffer(string: "NO")

        var maybeClient1: Channel? = nil
        XCTAssertNoThrow(maybeClient1 = try bootstrap.connect(to: server1.localAddress!).wait())
@ -387,6 +371,49 @@ final class NIOTSBootstrapTests: XCTestCase {
        XCTAssertEqual(try listenerChannel.getOption(NIOTSChannelOptions.multipathServiceType).wait(), .handover)
        XCTAssertEqual(try connectionChannel.getOption(NIOTSChannelOptions.multipathServiceType).wait(), .handover)
    }
+
+    func testNWParametersConfigurator() async throws {
+        try await withEventLoopGroup { group in
+            let configuratorServerListenerCounter = NIOLockedValueBox(0)
+            let configuratorServerConnectionCounter = NIOLockedValueBox(0)
+            let configuratorClientConnectionCounter = NIOLockedValueBox(0)
+            let waitForConnectionHandler = WaitForConnectionHandler(
+                connectionPromise: group.next().makePromise()
+            )
+
+            let listenerChannel = try await NIOTSListenerBootstrap(group: group)
+                .childChannelInitializer { connectionChannel in
+                    connectionChannel.eventLoop.makeCompletedFuture {
+                        try connectionChannel.pipeline.syncOperations.addHandler(waitForConnectionHandler)
+                    }
+                }
+                .configureNWParameters { _ in
+                    configuratorServerListenerCounter.withLockedValue { $0 += 1 }
+                }
+                .configureChildNWParameters { _ in
+                    configuratorServerConnectionCounter.withLockedValue { $0 += 1 }
+                }
+                .bind(host: "localhost", port: 0)
+                .get()
+
+            let connectionChannel: Channel = try await NIOTSConnectionBootstrap(group: group)
+                .configureNWParameters { _ in
+                    configuratorClientConnectionCounter.withLockedValue { $0 += 1 }
+                }
+                .connect(to: listenerChannel.localAddress!)
+                .get()
+
+            // Wait for the server to activate the connection channel to the client.
+            try await waitForConnectionHandler.connectionPromise.futureResult.get()
+
+            try await listenerChannel.close().get()
+            try await connectionChannel.close().get()
+
+            XCTAssertEqual(1, configuratorServerListenerCounter.withLockedValue { $0 })
+            XCTAssertEqual(1, configuratorServerConnectionCounter.withLockedValue { $0 })
+            XCTAssertEqual(1, configuratorClientConnectionCounter.withLockedValue { $0 })
+        }
+    }
 }

 extension Channel {
--- a/Tests/NIOTransportServicesTests/NIOTSChannelMetadataTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSChannelMetadataTests.swift
@ -37,13 +37,14 @@ final class NIOTSChannelMetadataTests: XCTestCase {
        }.wait()

    }
-    func testThowsIfCalledOnANonInitializedChannel() {
+    func testThrowsIfCalledOnANonInitializedChannel() {
        let eventLoopGroup = NIOTSEventLoopGroup()
        defer { XCTAssertNoThrow(try eventLoopGroup.syncShutdownGracefully()) }
        let channel = NIOTSConnectionChannel(
            eventLoop: eventLoopGroup.next() as! NIOTSEventLoop,
            tcpOptions: .init(),
-            tlsOptions: .init()
+            tlsOptions: .init(),
+            nwParametersConfigurator: nil
        )
        XCTAssertThrowsError(try channel.getMetadata(definition: NWProtocolTLS.definition).wait()) { error in
            XCTAssertTrue(error is NIOTSConnectionNotInitialized, "unexpected error \(error)")
--- a/Tests/NIOTransportServicesTests/NIOTSConnectionChannelTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSConnectionChannelTests.swift
@ -19,6 +19,7 @@ import NIOCore
 import NIOFoundationCompat
 import NIOTransportServices
 import Foundation
+import NIOConcurrencyHelpers

@available(macOS 10.14, iOS 12.0, tvOS 12.0, watchOS 6, *)
 final class ConnectRecordingHandler: ChannelOutboundHandler {
@ -73,13 +74,14 @@ final class DisableWaitingAfterConnect: ChannelOutboundHandler {
    typealias OutboundOut = Any

    func connect(context: ChannelHandlerContext, to address: SocketAddress, promise: EventLoopPromise<Void>?) {
+        do {
+            try context.channel.syncOptions?.setOption(NIOTSChannelOptions.waitForActivity, value: false)
+        } catch {
+            promise?.fail(error)
+            return
+        }

-        let f = context.channel.setOption(NIOTSChannelOptions.waitForActivity, value: false).flatMap {
-            context.connect(to: address)
-        }
-        if let promise = promise {
-            f.cascade(to: promise)
-        }
+        context.connect(to: address).cascade(to: promise)
    }
 }

@ -112,7 +114,7 @@ final class PromiseOnActiveHandler: ChannelInboundHandler {
 }

@available(OSX 10.14, iOS 12.0, tvOS 12.0, *)
-final class EventWaiter<Event>: ChannelInboundHandler {
+final class EventWaiter<Event: Sendable>: ChannelInboundHandler {
    typealias InboundIn = Any
    typealias InboundOut = Any

@ -145,7 +147,6 @@ class NIOTSConnectionChannelTests: XCTestCase {
    }

    func testConnectingToSocketAddressTraversesPipeline() throws {
-        let connectRecordingHandler = ConnectRecordingHandler()
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .bind(host: "localhost", port: 0).wait()
        defer {
@ -153,9 +154,14 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        let connectBootstrap = NIOTSConnectionBootstrap(group: self.group)
-            .channelInitializer { channel in channel.pipeline.addHandler(connectRecordingHandler) }
-        XCTAssertEqual(connectRecordingHandler.connectTargets, [])
-        XCTAssertEqual(connectRecordingHandler.endpointTargets, [])
+            .channelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let handler = ConnectRecordingHandler()
+                    try channel.pipeline.syncOperations.addHandler(handler)
+                    XCTAssertEqual(handler.connectTargets, [])
+                    XCTAssertEqual(handler.endpointTargets, [])
+                }
+            }

        let connection = try connectBootstrap.connect(to: listener.localAddress!).wait()
        defer {
@ -163,13 +169,13 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        try connection.eventLoop.submit {
-            XCTAssertEqual(connectRecordingHandler.connectTargets, [listener.localAddress!])
-            XCTAssertEqual(connectRecordingHandler.endpointTargets, [])
+            let handler = try connection.pipeline.syncOperations.handler(type: ConnectRecordingHandler.self)
+            XCTAssertEqual(handler.connectTargets, [listener.localAddress!])
+            XCTAssertEqual(handler.endpointTargets, [])
        }.wait()
    }

    func testConnectingToHostPortSkipsPipeline() throws {
-        let connectRecordingHandler = ConnectRecordingHandler()
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .bind(host: "localhost", port: 0).wait()
        defer {
@ -177,9 +183,14 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        let connectBootstrap = NIOTSConnectionBootstrap(group: self.group)
-            .channelInitializer { channel in channel.pipeline.addHandler(connectRecordingHandler) }
+            .channelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let connectRecordingHandler = ConnectRecordingHandler()
+                    try channel.pipeline.syncOperations.addHandler(connectRecordingHandler)
                    XCTAssertEqual(connectRecordingHandler.connectTargets, [])
                    XCTAssertEqual(connectRecordingHandler.endpointTargets, [])
+                }
+            }

        let connection = try connectBootstrap.connect(host: "localhost", port: Int(listener.localAddress!.port!)).wait()
        defer {
@ -187,6 +198,9 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        try connection.eventLoop.submit {
+            let connectRecordingHandler = try connection.pipeline.syncOperations.handler(
+                type: ConnectRecordingHandler.self
+            )
            XCTAssertEqual(connectRecordingHandler.connectTargets, [])
            XCTAssertEqual(
                connectRecordingHandler.endpointTargets,
@ -201,7 +215,6 @@ class NIOTSConnectionChannelTests: XCTestCase {
    }

    func testConnectingToEndpointSkipsPipeline() throws {
-        let connectRecordingHandler = ConnectRecordingHandler()
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .bind(host: "localhost", port: 0).wait()
        defer {
@ -209,9 +222,14 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        let connectBootstrap = NIOTSConnectionBootstrap(group: self.group)
-            .channelInitializer { channel in channel.pipeline.addHandler(connectRecordingHandler) }
+            .channelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let connectRecordingHandler = ConnectRecordingHandler()
+                    try channel.pipeline.syncOperations.addHandler(connectRecordingHandler)
                    XCTAssertEqual(connectRecordingHandler.connectTargets, [])
                    XCTAssertEqual(connectRecordingHandler.endpointTargets, [])
+                }
+            }

        let target = NWEndpoint.hostPort(
            host: "localhost",
@ -224,6 +242,9 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        try connection.eventLoop.submit {
+            let connectRecordingHandler = try connection.pipeline.syncOperations.handler(
+                type: ConnectRecordingHandler.self
+            )
            XCTAssertEqual(connectRecordingHandler.connectTargets, [])
            XCTAssertEqual(connectRecordingHandler.endpointTargets, [target])
        }.wait()
@ -231,7 +252,11 @@ class NIOTSConnectionChannelTests: XCTestCase {

    func testZeroLengthWritesHaveSatisfiedPromises() throws {
        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(FailOnReadHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(FailOnReadHandler())
+                }
+            }
            .bind(host: "localhost", port: 0).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -247,11 +272,15 @@ class NIOTSConnectionChannelTests: XCTestCase {
    }

    func testSettingTCPOptionsWholesale() throws {
-        let tcpOptions = NWProtocolTCP.Options()
-        tcpOptions.disableAckStretching = true
+        let listenerTCPOptions = NWProtocolTCP.Options()
+        listenerTCPOptions.disableAckStretching = true
+
+        let connectionTCPOptions = NWProtocolTCP.Options()
+        connectionTCPOptions.disableAckStretching = true

        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .tcpOptions(tcpOptions)
+            .tcpOptions(listenerTCPOptions)
+            .childTCPOptions(connectionTCPOptions)
            .serverChannelInitializer { channel in
                channel.getOption(ChannelOptions.socket(IPPROTO_TCP, TCP_SENDMOREACKS)).map { value in
                    XCTAssertEqual(value, 1)
@ -268,7 +297,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        let connection = try NIOTSConnectionBootstrap(group: self.group)
-            .tcpOptions(tcpOptions)
+            .tcpOptions(connectionTCPOptions)
            .channelInitializer { channel in
                channel.getOption(ChannelOptions.socket(IPPROTO_TCP, TCP_SENDMOREACKS)).map { value in
                    XCTAssertEqual(value, 1)
@ -320,13 +349,16 @@ class NIOTSConnectionChannelTests: XCTestCase {
            XCTAssertNoThrow(try listener.close().wait())
        }

-        var writabilities = [Bool]()
-        let handler = WritabilityChangedHandler { newValue in
-            writabilities.append(newValue)
-        }
-
+        let writabilities: NIOLockedValueBox<[Bool]> = .init([])
        let connection = try NIOTSConnectionBootstrap(group: self.group)
-            .channelInitializer { channel in channel.pipeline.addHandler(handler) }
+            .channelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let handler = WritabilityChangedHandler { newValue in
+                        writabilities.withLockedValue { $0.append(newValue) }
+                    }
+                    try channel.pipeline.syncOperations.addHandler(handler)
+                }
+            }
            .connect(to: listener.localAddress!)
            .wait()

@ -337,8 +369,6 @@ class NIOTSConnectionChannelTests: XCTestCase {
                value: ChannelOptions.Types.WriteBufferWaterMark(low: 2, high: 2048)
            ).wait()
        )
-        var buffer = connection.allocator.buffer(capacity: 2048)
-        buffer.writeBytes(repeatElement(UInt8(4), count: 2048))

        // We're going to issue the following pattern of writes:
        // a: 1 byte
@ -355,58 +385,61 @@ class NIOTSConnectionChannelTests: XCTestCase {
        // until after the promise for d has fired: by the time the promise for e has fired it will be writable
        // again.
        try connection.eventLoop.submit {
+            var buffer = connection.allocator.buffer(capacity: 2048)
+            buffer.writeBytes(repeatElement(UInt8(4), count: 2048))
+
            // Pre writing.
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)

            // Write a. After this write, we are still writable. When this write
            // succeeds, we'll still be not writable.
            connection.write(buffer.getSlice(at: 0, length: 1)).whenComplete { (_: Result<Void, Error>) in
-                XCTAssertEqual(writabilities, [false])
+                XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
                XCTAssertFalse(connection.isWritable)
            }
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)

            // Write b. After this write we are still writable. When this write
            // succeeds we'll still be not writable.
            connection.write(buffer.getSlice(at: 0, length: 1)).whenComplete { (_: Result<Void, Error>) in
-                XCTAssertEqual(writabilities, [false])
+                XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
                XCTAssertFalse(connection.isWritable)
            }
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)

            // Write c. After this write we are still writable (2047 bytes written).
            // When this write succeeds we'll still be not writable (2 bytes outstanding).
            connection.write(buffer.getSlice(at: 0, length: 2045)).whenComplete { (_: Result<Void, Error>) in
-                XCTAssertEqual(writabilities, [false])
+                XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
                XCTAssertFalse(connection.isWritable)
            }
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)

            // Write d. After this write we are still writable (2048 bytes written).
            // When this write succeeds we'll become writable, but critically the promise fires before
            // the state change, so we'll *appear* to be unwritable.
            connection.write(buffer.getSlice(at: 0, length: 1)).whenComplete { (_: Result<Void, Error>) in
-                XCTAssertEqual(writabilities, [false])
+                XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
                XCTAssertFalse(connection.isWritable)
            }
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)

            // Write e. After this write we are now not writable (2049 bytes written).
            // When this write succeeds we'll have already been writable, thanks to the previous
            // write.
            connection.write(buffer.getSlice(at: 0, length: 1)).whenComplete { (_: Result<Void, Error>) in
-                XCTAssertEqual(writabilities, [false, true])
+                XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false, true])
                XCTAssertTrue(connection.isWritable)

                // We close after this succeeds.
                connection.close(promise: nil)
            }
-            XCTAssertEqual(writabilities, [false])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
            XCTAssertFalse(connection.isWritable)
        }.wait()

@ -415,7 +448,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
        XCTAssertNoThrow(try connection.closeFuture.wait())

        // Ok, check that the writability changes worked.
-        XCTAssertEqual(writabilities, [false, true])
+        XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false, true])
    }

    func testWritabilityChangesAfterChangingWatermarks() throws {
@ -425,23 +458,22 @@ class NIOTSConnectionChannelTests: XCTestCase {
            XCTAssertNoThrow(try listener.close().wait())
        }

-        var writabilities = [Bool]()
-        let handler = WritabilityChangedHandler { newValue in
-            writabilities.append(newValue)
-        }
-
+        let writabilities: NIOLockedValueBox<[Bool]> = .init([])
        let connection = try NIOTSConnectionBootstrap(group: self.group)
-            .channelInitializer { channel in channel.pipeline.addHandler(handler) }
+            .channelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let handler = WritabilityChangedHandler { newValue in
+                        writabilities.withLockedValue({ $0.append(newValue) })
+                    }
+                    try channel.pipeline.syncOperations.addHandler(handler)
+                }
+            }
            .connect(to: listener.localAddress!)
            .wait()
        defer {
            XCTAssertNoThrow(try connection.close().wait())
        }

-        // We're going to allocate a buffer.
-        var buffer = connection.allocator.buffer(capacity: 256)
-        buffer.writeBytes(repeatElement(UInt8(4), count: 256))
-
        // We're going to issue a 256-byte write. This write will not cause any change in channel writability
        // state.
        //
@ -462,13 +494,17 @@ class NIOTSConnectionChannelTests: XCTestCase {
        //
        // Then we're going to set the high watermark to 1024, and the low to 256. This will change nothing.
        try connection.eventLoop.submit {
+            // We're going to allocate a buffer.
+            var buffer = connection.allocator.buffer(capacity: 256)
+            buffer.writeBytes(repeatElement(UInt8(4), count: 256))
+
            // Pre changes.
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)

            // Write. No writability change.
            connection.write(buffer, promise: nil)
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)
        }.wait()

@ -477,7 +513,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
            value: ChannelOptions.Types.WriteBufferWaterMark(low: 128, high: 256)
        ).flatMap {
            // High to 256, low to 128. No writability change.
-            XCTAssertEqual(writabilities, [])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [])
            XCTAssertTrue(connection.isWritable)

            return connection.setOption(
@ -486,7 +522,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
            )
        }.flatMap {
            // High to 255, low to 127. Channel becomes not writable.
-            XCTAssertEqual(writabilities, [false])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
            XCTAssertFalse(connection.isWritable)

            return connection.setOption(
@ -495,7 +531,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
            )
        }.flatMap {
            // High back to 256, low to 128. No writability change.
-            XCTAssertEqual(writabilities, [false])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
            XCTAssertFalse(connection.isWritable)

            return connection.setOption(
@ -504,7 +540,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
            )
        }.flatMap {
            // High to 1024, low to 128. No writability change.
-            XCTAssertEqual(writabilities, [false])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false])
            XCTAssertFalse(connection.isWritable)

            return connection.setOption(
@ -513,7 +549,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
            )
        }.flatMap {
            // Low to 257, channel becomes writable again.
-            XCTAssertEqual(writabilities, [false, true])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false, true])
            XCTAssertTrue(connection.isWritable)

            return connection.setOption(
@ -522,7 +558,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
            )
        }.map {
            // Low back to 256, no writability change.
-            XCTAssertEqual(writabilities, [false, true])
+            XCTAssertEqual(writabilities.withLockedValue({ $0 }), [false, true])
            XCTAssertTrue(connection.isWritable)
        }.wait()
    }
@ -608,7 +644,9 @@ class NIOTSConnectionChannelTests: XCTestCase {
    func testEarlyExitCanBeSetInWaitingState() throws {
        let connectFuture = NIOTSConnectionBootstrap(group: self.group)
            .channelInitializer { channel in
-                channel.pipeline.addHandler(DisableWaitingAfterConnect())
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(DisableWaitingAfterConnect())
+                }
            }.connect(to: try SocketAddress(unixDomainSocketPath: "/this/path/definitely/doesnt/exist"))

        do {
@ -712,7 +750,11 @@ class NIOTSConnectionChannelTests: XCTestCase {

        let channel = try NIOTSConnectionBootstrap(group: self.group)
            .channelInitializer { channel in
-                channel.pipeline.addHandler(PromiseOnActiveHandler(activePromise))
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(
+                        PromiseOnActiveHandler(activePromise)
+                    )
+                }
            }.connect(to: listener.localAddress!).wait()

        XCTAssertNoThrow(try activePromise.futureResult.wait())
@ -772,10 +814,13 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        let testCompletePromise = self.group.next().makePromise(of: Void.self)
-        let testHandler = TestHandler(testCompletePromise: testCompletePromise)
        let listener = try assertNoThrowWithValue(
            NIOTSListenerBootstrap(group: self.group)
-                .childChannelInitializer { channel in channel.pipeline.addHandler(EchoHandler()) }
+                .childChannelInitializer { channel in
+                    channel.eventLoop.makeCompletedFuture {
+                        try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                    }
+                }
                .bind(host: "localhost", port: 0).wait()
        )
        defer {
@ -783,7 +828,13 @@ class NIOTSConnectionChannelTests: XCTestCase {
        }

        let connectBootstrap = NIOTSConnectionBootstrap(group: self.group)
-            .channelInitializer { channel in channel.pipeline.addHandler(testHandler) }
+            .channelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(
+                        TestHandler(testCompletePromise: testCompletePromise)
+                    )
+                }
+            }

        let connection = try assertNoThrowWithValue(connectBootstrap.connect(to: listener.localAddress!).wait())
        defer {
@ -804,7 +855,8 @@ class NIOTSConnectionChannelTests: XCTestCase {
        // We expect 2.
        XCTAssertNoThrow(
            try connection.eventLoop.submit {
-                XCTAssertEqual(testHandler.readCount, 2)
+                let handler = try connection.pipeline.syncOperations.handler(type: TestHandler.self)
+                XCTAssertEqual(handler.readCount, 2)
            }.wait()
        )
    }
@ -839,11 +891,15 @@ class NIOTSConnectionChannelTests: XCTestCase {
    func testConnectingInvolvesWaiting() throws {
        let loop = self.group.next()
        let eventPromise = loop.makePromise(of: NIOTSNetworkEvents.WaitingForConnectivity.self)
-        let eventRecordingHandler = EventWaiter<NIOTSNetworkEvents.WaitingForConnectivity>(eventPromise)

        // 5s is the worst-case test time: normally it'll be faster as we don't wait for this.
        let connectBootstrap = NIOTSConnectionBootstrap(group: loop)
-            .channelInitializer { channel in channel.pipeline.addHandler(eventRecordingHandler) }
+            .channelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let eventRecordingHandler = EventWaiter<NIOTSNetworkEvents.WaitingForConnectivity>(eventPromise)
+                    try channel.pipeline.syncOperations.addHandler(eventRecordingHandler)
+                }
+            }
            .connectTimeout(.seconds(5))

        // We choose 443 here to avoid triggering Private Relay, which can do all kinds of weird stuff to this test.
@ -868,7 +924,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
    }

    func testSyncOptionsAreSupported() throws {
-        func testSyncOptions(_ channel: Channel) {
+        @Sendable func testSyncOptions(_ channel: Channel) {
            if let sync = channel.syncOptions {
                do {
                    let autoRead = try sync.getOption(ChannelOptions.autoRead)
@ -919,6 +975,7 @@ class NIOTSConnectionChannelTests: XCTestCase {
            func channelActive(context: ChannelHandlerContext) {
                listenerChannel
                    .close()
+                    .assumeIsolated()
                    .whenSuccess { _ in
                        _ = context.channel.write(ByteBuffer(data: Data()))
                    }
@ -943,13 +1000,15 @@ class NIOTSConnectionChannelTests: XCTestCase {
        let testCompletePromise = self.group.next().makePromise(of: Error.self)
        let connection = try NIOTSConnectionBootstrap(group: self.group)
            .channelInitializer { channel in
-                channel.pipeline.addHandler(
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(
                        ForwardErrorHandler(
                            testCompletePromise: testCompletePromise,
                            listenerChannel: listener
                        )
                    )
                }
+            }
            .connect(to: listener.localAddress!)
            .wait()
        XCTAssertNoThrow(try connection.close().wait())
--- a/Tests/NIOTransportServicesTests/NIOTSDatagramConnectionChannelTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSDatagramConnectionChannelTests.swift
@ -18,9 +18,10 @@ import Network
 import NIOCore
 import NIOTransportServices
 import Foundation
+import NIOConcurrencyHelpers

 extension Channel {
-    func wait<T>(for type: T.Type, count: Int) throws -> [T] {
+    func wait<T: Sendable>(for type: T.Type, count: Int) throws -> [T] {
        try self.pipeline.context(name: "ByteReadRecorder").flatMap { context in
            if let future = (context.handler as? ReadRecorder<T>)?.notifyForDatagrams(count) {
                return future
@ -53,7 +54,7 @@ extension Channel {
    }
 }

-final class ReadRecorder<DataType>: ChannelInboundHandler {
+final class ReadRecorder<DataType: Sendable>: ChannelInboundHandler {
    typealias InboundIn = DataType
    typealias InboundOut = DataType

@ -113,29 +114,42 @@ final class ReadRecorder<DataType>: ChannelInboundHandler {

 // Mimicks the DatagramChannelTest from apple/swift-nio
@available(macOS 10.14, iOS 12.0, tvOS 12.0, watchOS 6, *)
-final class NIOTSDatagramConnectionChannelTests: XCTestCase {
+final class NIOTSDatagramBootstrapTests: XCTestCase {
    private var group: NIOTSEventLoopGroup!

    private func buildServerChannel(
        group: NIOTSEventLoopGroup,
        host: String = "127.0.0.1",
        port: Int = 0,
-        onConnect: @escaping (Channel) -> Void
+        onConnect: @escaping @Sendable (Channel) -> Void
    ) throws -> Channel {
        try NIOTSDatagramListenerBootstrap(group: group)
            .childChannelInitializer { childChannel in
                onConnect(childChannel)
-                return childChannel.pipeline.addHandler(ReadRecorder<ByteBuffer>(), name: "ByteReadRecorder")
+                return childChannel.eventLoop.makeCompletedFuture {
+                    try childChannel.pipeline.syncOperations.addHandler(
+                        ReadRecorder<ByteBuffer>(),
+                        name: "ByteReadRecorder"
+                    )
+                }
            }
            .bind(host: host, port: port)
            .wait()
    }

-    private func buildClientChannel(group: NIOTSEventLoopGroup, host: String = "127.0.0.1", port: Int) throws -> Channel
-    {
-        try NIOTSDatagramBootstrap(group: group)
+    private func buildClientChannel(
+        group: NIOTSEventLoopGroup,
+        host: String = "127.0.0.1",
+        port: Int
+    ) throws -> Channel {
+        try NIOTSDatagramConnectionBootstrap(group: group)
            .channelInitializer { channel in
-                channel.pipeline.addHandler(ReadRecorder<ByteBuffer>(), name: "ByteReadRecorder")
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(
+                        ReadRecorder<ByteBuffer>(),
+                        name: "ByteReadRecorder"
+                    )
+                }
            }
            .connect(host: host, port: port)
            .wait()
@ -169,7 +183,7 @@ final class NIOTSDatagramConnectionChannelTests: XCTestCase {
    }

    func testSyncOptionsAreSupported() throws {
-        func testSyncOptions(_ channel: Channel) {
+        @Sendable func testSyncOptions(_ channel: Channel) {
            if let sync = channel.syncOptions {
                do {
                    let endpointReuse = try sync.getOption(NIOTSChannelOptions.allowLocalEndpointReuse)
@ -192,7 +206,12 @@ final class NIOTSDatagramConnectionChannelTests: XCTestCase {
            .childChannelInitializer { channel in
                testSyncOptions(channel)
                promise.succeed(channel)
-                return channel.pipeline.addHandler(ReadRecorder<ByteBuffer>(), name: "ByteReadRecorder")
+                return channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(
+                        ReadRecorder<ByteBuffer>(),
+                        name: "ByteReadRecorder"
+                    )
+                }
            }
            .bind(host: "localhost", port: 0)
            .wait()
@ -200,7 +219,7 @@ final class NIOTSDatagramConnectionChannelTests: XCTestCase {
            XCTAssertNoThrow(try listener.close().wait())
        }

-        let connection = try! NIOTSDatagramBootstrap(group: self.group)
+        let connection = try! NIOTSDatagramConnectionBootstrap(group: self.group)
            .channelInitializer { channel in
                testSyncOptions(channel)
                return channel.eventLoop.makeSucceededVoidFuture()
@ -214,6 +233,54 @@ final class NIOTSDatagramConnectionChannelTests: XCTestCase {
        XCTAssertNoThrow(try connection.close().wait())
    }

+    func testNWParametersConfigurator() async throws {
+        try await withEventLoopGroup { group in
+            let configuratorServerListenerCounter = NIOLockedValueBox(0)
+            let configuratorServerConnectionCounter = NIOLockedValueBox(0)
+            let configuratorClientConnectionCounter = NIOLockedValueBox(0)
+            let waitForConnectionHandler = WaitForConnectionHandler(
+                connectionPromise: group.next().makePromise()
+            )
+
+            let listenerChannel = try await NIOTSDatagramListenerBootstrap(group: group)
+                .childChannelInitializer { connectionChannel in
+                    connectionChannel.eventLoop.makeCompletedFuture {
+                        try connectionChannel.pipeline.syncOperations.addHandler(waitForConnectionHandler)
+                    }
+                }
+                .configureNWParameters { _ in
+                    configuratorServerListenerCounter.withLockedValue { $0 += 1 }
+                }
+                .configureChildNWParameters { _ in
+                    configuratorServerConnectionCounter.withLockedValue { $0 += 1 }
+                }
+                .bind(host: "localhost", port: 0)
+                .get()
+
+            let connectionChannel: Channel = try await NIOTSDatagramConnectionBootstrap(group: group)
+                .configureNWParameters { _ in
+                    configuratorClientConnectionCounter.withLockedValue { $0 += 1 }
+                }
+                .connect(to: listenerChannel.localAddress!)
+                .get()
+
+            // Need to write something so the server can activate the connection channel: this is UDP,
+            // so there is no handshaking that happens and thus the server cannot know that the
+            // connection has been established and the channel can be activated until we receive something.
+            try await connectionChannel.writeAndFlush(ByteBuffer(bytes: [42]))
+
+            // Wait for the server to activate the connection channel to the client.
+            try await waitForConnectionHandler.connectionPromise.futureResult.get()
+
+            try await listenerChannel.close().get()
+            try await connectionChannel.close().get()
+
+            XCTAssertEqual(1, configuratorServerListenerCounter.withLockedValue { $0 })
+            XCTAssertEqual(1, configuratorServerConnectionCounter.withLockedValue { $0 })
+            XCTAssertEqual(1, configuratorClientConnectionCounter.withLockedValue { $0 })
+        }
+    }
+
    func testCanExtractTheConnection() throws {
        guard #available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *) else {
            throw XCTSkip("Option not available")
@ -225,7 +292,7 @@ final class NIOTSDatagramConnectionChannelTests: XCTestCase {
            XCTAssertNoThrow(try listener.close().wait())
        }

-        _ = try NIOTSDatagramBootstrap(group: self.group)
+        _ = try NIOTSDatagramConnectionBootstrap(group: self.group)
            .channelInitializer { channel in
                let conn = try! channel.syncOptions!.getOption(NIOTSChannelOptions.connection)
                XCTAssertNil(conn)
--- a/Tests/NIOTransportServicesTests/NIOTSEndToEndTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSEndToEndTests.swift
@ -18,6 +18,7 @@ import NIOCore
 import NIOTransportServices
 import Foundation
 import Network
+import NIOConcurrencyHelpers

 func assertNoThrowWithValue<T>(
    _ body: @autoclosure () throws -> T,
@ -56,44 +57,29 @@ final class ReadExpecter: ChannelInboundHandler {

    struct DidNotReadError: Error {}

-    private var readPromise: EventLoopPromise<Void>?
+    private let readPromise: EventLoopPromise<Void>
    private var cumulationBuffer: ByteBuffer?
    private let expectedRead: ByteBuffer

-    var readFuture: EventLoopFuture<Void>? {
-        self.readPromise?.futureResult
-    }
-
-    init(expecting: ByteBuffer) {
+    init(expecting: ByteBuffer, readPromise: EventLoopPromise<Void>) {
+        self.readPromise = readPromise
+        self.cumulationBuffer = nil
        self.expectedRead = expecting
    }

-    func handlerAdded(context: ChannelHandlerContext) {
-        self.readPromise = context.eventLoop.makePromise()
-    }
-
    func handlerRemoved(context: ChannelHandlerContext) {
-        if let promise = self.readPromise {
-            promise.fail(DidNotReadError())
-        }
+        self.readPromise.fail(DidNotReadError())
    }

    func channelRead(context: ChannelHandlerContext, data: NIOAny) {
        var bytes = self.unwrapInboundIn(data)
-        if self.cumulationBuffer == nil {
-            self.cumulationBuffer = bytes
-        } else {
-            self.cumulationBuffer!.writeBuffer(&bytes)
-        }
-
+        self.cumulationBuffer.setOrWriteBuffer(&bytes)
        self.maybeFulfillPromise()
    }

    private func maybeFulfillPromise() {
-        if let promise = self.readPromise, self.cumulationBuffer! == self.expectedRead {
-            promise.succeed(())
-            self.readPromise = nil
-        }
+        guard self.cumulationBuffer == self.expectedRead else { return }
+        self.readPromise.succeed(())
    }
 }

@ -180,9 +166,12 @@ final class WaitForActiveHandler: ChannelInboundHandler {
 extension Channel {
    /// Expect that the given bytes will be received.
    func expectRead(_ bytes: ByteBuffer) -> EventLoopFuture<Void> {
-        let expecter = ReadExpecter(expecting: bytes)
-        return self.pipeline.addHandler(expecter).flatMap {
-            expecter.readFuture!
+        let readPromise = self.eventLoop.makePromise(of: Void.self)
+        return self.eventLoop.submit {
+            let expecter = ReadExpecter(expecting: bytes, readPromise: readPromise)
+            try self.pipeline.syncOperations.addHandler(expecter)
+        }.flatMap {
+            readPromise.futureResult
        }
    }
 }
@ -209,7 +198,11 @@ class NIOTSEndToEndTests: XCTestCase {

    func testSimpleListener() throws {
        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(EchoHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                }
+            }
            .bind(host: "localhost", port: 0).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -232,7 +225,11 @@ class NIOTSEndToEndTests: XCTestCase {
            on: NWEndpoint.Port(rawValue: 0)!
        )
        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(EchoHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                }
+            }
            .withNWListener(nwListenerTest).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -259,7 +256,11 @@ class NIOTSEndToEndTests: XCTestCase {

    func testMultipleConnectionsOneListener() throws {
        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(EchoHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                }
+            }
            .bind(host: "localhost", port: 0).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -282,7 +283,11 @@ class NIOTSEndToEndTests: XCTestCase {

    func testBasicConnectionTeardown() throws {
        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(CloseOnActiveHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(CloseOnActiveHandler())
+                }
+            }
            .bind(host: "localhost", port: 0).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -304,12 +309,12 @@ class NIOTSEndToEndTests: XCTestCase {
        // This test is a little bit dicey, but we need 20 futures in this list.
        let closeFutureSyncQueue = DispatchQueue(label: "closeFutureSyncQueue")
        let closeFutureGroup = DispatchGroup()
-        var closeFutures: [EventLoopFuture<Void>] = []
+        let closeFutures: NIOLockedValueBox<[EventLoopFuture<Void>]> = .init([])

        let listener = try NIOTSListenerBootstrap(group: self.group)
            .childChannelInitializer { channel in
                closeFutureSyncQueue.sync {
-                    closeFutures.append(channel.closeFuture)
+                    closeFutures.withLockedValue { $0.append(channel.closeFuture) }
                }
                closeFutureGroup.leave()
                return channel.eventLoop.makeSucceededFuture(())
@ -320,7 +325,9 @@ class NIOTSEndToEndTests: XCTestCase {
        }

        let bootstrap = NIOTSConnectionBootstrap(group: self.group).channelInitializer { channel in
-            channel.pipeline.addHandler(CloseOnActiveHandler())
+            channel.eventLoop.makeCompletedFuture {
+                try channel.pipeline.syncOperations.addHandler(CloseOnActiveHandler())
+            }
        }

        for _ in (0..<10) {
@ -330,7 +337,7 @@ class NIOTSEndToEndTests: XCTestCase {
            closeFutureGroup.enter()
            bootstrap.connect(to: listener.localAddress!).whenSuccess { channel in
                closeFutureSyncQueue.sync {
-                    closeFutures.append(channel.closeFuture)
+                    closeFutures.withLockedValue { $0.append(channel.closeFuture) }
                }
                closeFutureGroup.leave()
            }
@ -338,7 +345,9 @@ class NIOTSEndToEndTests: XCTestCase {

        closeFutureGroup.wait()
        let allClosed = closeFutureSyncQueue.sync {
-            EventLoopFuture<Void>.andAllComplete(closeFutures, on: self.group.next())
+            closeFutures.withLockedValue {
+                EventLoopFuture<Void>.andAllComplete($0, on: self.group.next())
+            }
        }
        XCTAssertNoThrow(try allClosed.wait())
    }
@ -347,11 +356,13 @@ class NIOTSEndToEndTests: XCTestCase {
        let serverSideConnectionPromise: EventLoopPromise<Channel> = self.group.next().makePromise()
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .childChannelInitializer { channel in
-                channel.pipeline.addHandlers([
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandlers([
                        WaitForActiveHandler(serverSideConnectionPromise),
                        EchoHandler(),
                    ])
                }
+            }
            .bind(host: "localhost", port: 0).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -373,8 +384,9 @@ class NIOTSEndToEndTests: XCTestCase {
        let halfClosedPromise: EventLoopPromise<Void> = self.group.next().makePromise()
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .childChannelInitializer { channel in
-                channel.pipeline.addHandler(EchoHandler()).flatMap { _ in
-                    channel.pipeline.addHandler(HalfCloseHandler(halfClosedPromise))
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                    try channel.pipeline.syncOperations.addHandler(HalfCloseHandler(halfClosedPromise))
                }
            }
            .childChannelOption(ChannelOptions.allowRemoteHalfClosure, value: true)
@ -403,8 +415,9 @@ class NIOTSEndToEndTests: XCTestCase {
    func testDisabledHalfClosureCausesFullClosure() throws {
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .childChannelInitializer { channel in
-                channel.pipeline.addHandler(EchoHandler()).flatMap { _ in
-                    channel.pipeline.addHandler(FailOnHalfCloseHandler())
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                    try channel.pipeline.syncOperations.addHandler(FailOnHalfCloseHandler())
                }
            }
            .bind(host: "localhost", port: 0).wait()
@ -483,7 +496,11 @@ class NIOTSEndToEndTests: XCTestCase {
        let udsPath = "/tmp/\(UUID().uuidString)_testBasicUnixSockets.sock"

        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(EchoHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                }
+            }
            .bind(unixDomainSocketPath: udsPath).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -513,7 +530,11 @@ class NIOTSEndToEndTests: XCTestCase {
        let serviceEndpoint = NWEndpoint.service(name: name, type: "_niots._tcp", domain: "local", interface: nil)

        let listener = try NIOTSListenerBootstrap(group: self.group)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(EchoHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(EchoHandler())
+                }
+            }
            .bind(endpoint: serviceEndpoint).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -541,7 +562,11 @@ class NIOTSEndToEndTests: XCTestCase {
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .serverChannelOption(ChannelOptions.socket(SOL_SOCKET, SO_REUSEADDR), value: 0)
            .serverChannelOption(ChannelOptions.socket(SOL_SOCKET, SO_REUSEPORT), value: 0)
-            .childChannelInitializer { channel in channel.pipeline.addHandler(CloseOnActiveHandler()) }
+            .childChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(CloseOnActiveHandler())
+                }
+            }
            .bind(host: "localhost", port: 0).wait()
        let address = listener.localAddress!

@ -587,12 +612,12 @@ class NIOTSEndToEndTests: XCTestCase {
        let testCompletePromise = self.group.next().makePromise(of: Bool.self)
        let connection = try NIOTSConnectionBootstrap(group: self.group)
            .channelInitializer { channel in
-                channel.pipeline.addHandler(
-                    ViabilityHandler(
-                        testCompletePromise: testCompletePromise
-                    )
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(
+                        ViabilityHandler(testCompletePromise: testCompletePromise)
                    )
                }
+            }
            .connect(to: listener.localAddress!)
            .wait()

--- a/Tests/NIOTransportServicesTests/NIOTSEventLoopTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSEventLoopTests.swift
@ -147,7 +147,9 @@ class NIOTSEventLoopTest: XCTestCase {
    func testIndividualLoopsCannotBeShutDownWhenPartOfGroup() async throws {
        let group = NIOTSEventLoopGroup(loopCount: 3)
        defer {
-            try! group.syncShutdownGracefully()
+            Task {
+                try! await group.shutdownGracefully()
+            }
        }

        for loop in group.makeIterator() {
--- a/Tests/NIOTransportServicesTests/NIOTSListenerChannelTests.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSListenerChannelTests.swift
@ -55,13 +55,18 @@ class NIOTSListenerChannelTests: XCTestCase {
    }

    func testBindingToSocketAddressTraversesPipeline() throws {
-        let bindRecordingHandler = BindRecordingHandler()
        let target = try SocketAddress.makeAddressResolvingHost("localhost", port: 0)
        let bindBootstrap = NIOTSListenerBootstrap(group: self.group)
-            .serverChannelInitializer { channel in channel.pipeline.addHandler(bindRecordingHandler) }
-
+            .serverChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let bindRecordingHandler = BindRecordingHandler()
+                    try channel.pipeline.syncOperations.addHandler(
+                        bindRecordingHandler
+                    )
                    XCTAssertEqual(bindRecordingHandler.bindTargets, [])
                    XCTAssertEqual(bindRecordingHandler.endpointTargets, [])
+                }
+            }

        let listener = try bindBootstrap.bind(to: target).wait()
        defer {
@ -69,18 +74,22 @@ class NIOTSListenerChannelTests: XCTestCase {
        }

        try self.group.next().submit {
-            XCTAssertEqual(bindRecordingHandler.bindTargets, [target])
-            XCTAssertEqual(bindRecordingHandler.endpointTargets, [])
+            let handler = try listener.pipeline.syncOperations.handler(type: BindRecordingHandler.self)
+            XCTAssertEqual(handler.bindTargets, [target])
+            XCTAssertEqual(handler.endpointTargets, [])
        }.wait()
    }

    func testConnectingToHostPortTraversesPipeline() throws {
-        let bindRecordingHandler = BindRecordingHandler()
        let bindBootstrap = NIOTSListenerBootstrap(group: self.group)
-            .serverChannelInitializer { channel in channel.pipeline.addHandler(bindRecordingHandler) }
-
+            .serverChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let bindRecordingHandler = BindRecordingHandler()
+                    try channel.pipeline.syncOperations.addHandler(bindRecordingHandler)
                    XCTAssertEqual(bindRecordingHandler.bindTargets, [])
                    XCTAssertEqual(bindRecordingHandler.endpointTargets, [])
+                }
+            }

        let listener = try bindBootstrap.bind(host: "localhost", port: 0).wait()
        defer {
@ -88,22 +97,28 @@ class NIOTSListenerChannelTests: XCTestCase {
        }

        try self.group.next().submit {
+            let handler = try listener.pipeline.syncOperations.handler(
+                type: BindRecordingHandler.self
+            )
            XCTAssertEqual(
-                bindRecordingHandler.bindTargets,
+                handler.bindTargets,
                [try SocketAddress.makeAddressResolvingHost("localhost", port: 0)]
            )
-            XCTAssertEqual(bindRecordingHandler.endpointTargets, [])
+            XCTAssertEqual(handler.endpointTargets, [])
        }.wait()
    }

    func testConnectingToEndpointSkipsPipeline() throws {
        let endpoint = NWEndpoint.hostPort(host: .ipv4(.loopback), port: .any)
-        let bindRecordingHandler = BindRecordingHandler()
        let bindBootstrap = NIOTSListenerBootstrap(group: self.group)
-            .serverChannelInitializer { channel in channel.pipeline.addHandler(bindRecordingHandler) }
-
+            .serverChannelInitializer { channel in
+                channel.eventLoop.makeCompletedFuture {
+                    let bindRecordingHandler = BindRecordingHandler()
+                    try channel.pipeline.syncOperations.addHandler(bindRecordingHandler)
                    XCTAssertEqual(bindRecordingHandler.bindTargets, [])
                    XCTAssertEqual(bindRecordingHandler.endpointTargets, [])
+                }
+            }

        let listener = try bindBootstrap.bind(endpoint: endpoint).wait()
        defer {
@ -111,8 +126,11 @@ class NIOTSListenerChannelTests: XCTestCase {
        }

        try self.group.next().submit {
-            XCTAssertEqual(bindRecordingHandler.bindTargets, [])
-            XCTAssertEqual(bindRecordingHandler.endpointTargets, [endpoint])
+            let handler = try listener.pipeline.syncOperations.handler(
+                type: BindRecordingHandler.self
+            )
+            XCTAssertEqual(handler.bindTargets, [])
+            XCTAssertEqual(handler.endpointTargets, [endpoint])
        }.wait()
    }

@ -169,7 +187,11 @@ class NIOTSListenerChannelTests: XCTestCase {
        let listener = try NIOTSListenerBootstrap(group: self.group, childGroup: childGroup)
            .childChannelInitializer { channel in
                childChannelPromise.succeed(channel)
-                return channel.pipeline.addHandler(PromiseOnActiveHandler(activePromise))
+                return channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(
+                        PromiseOnActiveHandler(activePromise)
+                    )
+                }
            }.bind(host: "localhost", port: 0).wait()
        defer {
            XCTAssertNoThrow(try listener.close().wait())
@ -243,7 +265,9 @@ class NIOTSListenerChannelTests: XCTestCase {
        let channelPromise = self.group.next().makePromise(of: Channel.self)
        let listener = try NIOTSListenerBootstrap(group: self.group)
            .serverChannelInitializer { channel in
-                channel.pipeline.addHandler(ChannelReceiver(channelPromise))
+                channel.eventLoop.makeCompletedFuture {
+                    try channel.pipeline.syncOperations.addHandler(ChannelReceiver(channelPromise))
+                }
            }
            .bind(host: "localhost", port: 0).wait()
        defer {
@ -258,7 +282,9 @@ class NIOTSListenerChannelTests: XCTestCase {
        // We must wait for channel active here, or the socket addresses won't be set.
        let promisedChannel = try channelPromise.futureResult.flatMap { (channel) -> EventLoopFuture<Channel> in
            let promiseChannelActive = channel.eventLoop.makePromise(of: Channel.self)
-            _ = channel.pipeline.addHandler(WaitForActiveHandler(promiseChannelActive))
+            try? channel.pipeline.syncOperations.addHandler(
+                WaitForActiveHandler(promiseChannelActive)
+            )
            return promiseChannelActive.futureResult
        }.wait()

@ -314,7 +340,7 @@ class NIOTSListenerChannelTests: XCTestCase {
    }

    func testSyncOptionsAreSupported() throws {
-        func testSyncOptions(_ channel: Channel) {
+        @Sendable func testSyncOptions(_ channel: Channel) {
            if let sync = channel.syncOptions {
                do {
                    let endpointReuse = try sync.getOption(NIOTSChannelOptions.allowLocalEndpointReuse)
--- a/Tests/NIOTransportServicesTests/NIOTSTestUtilities.swift
+++ b/Tests/NIOTransportServicesTests/NIOTSTestUtilities.swift
@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2017-2025 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+#if canImport(Network)
+import NIOCore
+import NIOTransportServices
+
+func withEventLoopGroup(_ test: (EventLoopGroup) async throws -> Void) async rethrows {
+    let group = NIOTSEventLoopGroup()
+    do {
+        try await test(group)
+        try? await group.shutdownGracefully()
+    } catch {
+        try? await group.shutdownGracefully()
+        throw error
+    }
+}
+
+final class WaitForConnectionHandler: ChannelInboundHandler, Sendable {
+    typealias InboundIn = Never
+
+    let connectionPromise: EventLoopPromise<Void>
+
+    init(connectionPromise: EventLoopPromise<Void>) {
+        self.connectionPromise = connectionPromise
+    }
+
+    func channelActive(context: ChannelHandlerContext) {
+        self.connectionPromise.succeed()
+        context.fireChannelActive()
+    }
+}
+#endif
--- a/docker/docker-compose.2004.main.yaml
+++ b/docker/docker-compose.2004.main.yaml
@ -0,0 +1,60 @@
+version: "3"
+
+services:
+
+  runtime-setup:
+    image: swift-nio:20.04-main
+    build:
+      args:
+        base_image: "swiftlang/swift:nightly-main-focal"
+        ubuntu_version: "focal"
+
+  unit-tests:
+    image: swift-nio:20.04-main
+
+  integration-tests:
+    image: swift-nio:20.04-main
+
+  test:
+    image: swift-nio:20.04-main
+    environment:
+      - MAX_ALLOCS_ALLOWED_1000_addHandlers=47050
+      - MAX_ALLOCS_ALLOWED_1000_addHandlers_sync=40050
+      - MAX_ALLOCS_ALLOWED_1000_getHandlers=12050
+      - MAX_ALLOCS_ALLOWED_1000_getHandlers_sync=50
+      - MAX_ALLOCS_ALLOWED_1000_reqs_1_conn=30540
+      - MAX_ALLOCS_ALLOWED_1000_tcpbootstraps=4100
+      - MAX_ALLOCS_ALLOWED_1000_tcpconnections=179010
+      - MAX_ALLOCS_ALLOWED_1000_udp_reqs=16050
+      - MAX_ALLOCS_ALLOWED_1000_udpbootstraps=2000
+      - MAX_ALLOCS_ALLOWED_1000_udpconnections=101050
+      - MAX_ALLOCS_ALLOWED_1_reqs_1000_conn=471050
+      - MAX_ALLOCS_ALLOWED_bytebuffer_lots_of_rw=2100
+      - MAX_ALLOCS_ALLOWED_creating_10000_headers=100
+      - MAX_ALLOCS_ALLOWED_decode_1000_ws_frames=2000
+      - MAX_ALLOCS_ALLOWED_encode_1000_ws_frames_holding_buffer=1000
+      - MAX_ALLOCS_ALLOWED_encode_1000_ws_frames_holding_buffer_with_space=1000
+      - MAX_ALLOCS_ALLOWED_encode_1000_ws_frames_new_buffer=5010
+      - MAX_ALLOCS_ALLOWED_encode_1000_ws_frames_new_buffer_with_space=5010
+      - MAX_ALLOCS_ALLOWED_future_lots_of_callbacks=75010
+      - MAX_ALLOCS_ALLOWED_modifying_1000_circular_buffer_elements=50
+      - MAX_ALLOCS_ALLOWED_modifying_byte_buffer_view=2010
+      - MAX_ALLOCS_ALLOWED_ping_pong_1000_reqs_1_conn=4440
+      - MAX_ALLOCS_ALLOWED_read_10000_chunks_from_file=190500
+      - MAX_ALLOCS_ALLOWED_schedule_10000_tasks=90050
+      - MAX_ALLOCS_ALLOWED_scheduling_10000_executions=20150
+      - MAX_ALLOCS_ALLOWED_udp_1000_reqs_1_conn=16250
+      - MAX_ALLOCS_ALLOWED_udp_1_reqs_1000_conn=202050
+      - SANITIZER_ARG=--sanitize=thread
+
+  performance-test:
+    image: swift-nio:20.04-main
+
+  shell:
+    image: swift-nio:20.04-main
+
+  echo:
+    image: swift-nio:20.04-main
+
+  http:
+    image: swift-nio:20.04-main
Author	SHA1	Message	Date
Johannes Weiss	7c21367b1a	Merge `862378ee24` into `7114435533`	2025-05-05 23:27:13 +00:00
Rick Newton-Rogers	7114435533	Drop Swift 5.9 (#235 ) Motivation: Swift 5.9 is no longer supported, we should bump the tools version and remove it from our CI. Modifications: * Bump the Swift tools version to Swift 5.10 * Remove Swift 5.9 jobs where appropriate in main.yml, pull_request.yml Result: Code reflects our support window.	2025-05-05 12:13:58 +01:00
Gus Cairo	d8443227d1	Change naming of datagram-related types to make them more consistent + fix docs (#233 ) ### Motivation: The datagram-related types logically mirror the TCP-based ones (`NIOTSDatagramListenerBootstrap` vs `NIOTSListenerBootstrap`; `NIOTSListenerChannel` vs `NIOTSDatagramListenerChannel`; `NIOTSDatagramChannel` vs `NIOTSDatagramConnectionChannel`; `NIOTSDatagramBootstrap` vs `NIOTSConnectionBootstrap`). However, some of the type names could more closely resemble their TCP counterparts to make it easier to navigate the code/understand what their purpose is. Additionally, the docs for some of these types are wrong, as they've been copy-pasted into the datagram versions without changes. ### Modifications: There are separate commits for each of the following changes: - Fix docs for `NIOTSDatagramListenerBootstrap` and rename the file to match the type name. - Rename `NIOTSDatagramConnectionChannelTests` to `NIOTSDatagramBootstrapTests` (to match `NIOTSBootstrapTests`). - Rename `NIOTSDatagramChannel` to `NIOTSDatagramConnectionChannel` (to match `NIOTSConnectionChannel`) - Fix docs for `NIOTSConnectionBootstrap`. - Rename `NIOTSDatagramBootstrap` to `NIOTSDatagramConnectionBootstrap` (to match `NIOTSConnectionBootstrap`). This one required a deprecate and replace since it's a public type. ### Result: Better docs and more consistency in our type names.	2025-04-29 13:56:21 +01:00
Gus Cairo	cd1e89816d	Add `NWParameters` configurator to bootstraps (#230 ) Allow users to provide a closure taking an `NWParameters` to customise them before they're used to create `NWConnection`s. ### Motivation: `NWParameters` are currently created using the provided TLS and UDP options, and then passed over to new `NWConnection`s. However, there are more ways in which `NWParameters` can be customised, so this new API provides a way for users to do this. ### Modifications: Introduce new `configureNWParameters` methods to the existing bootstraps to allow configuring a closure for customising `NWParameters`. ### Result: Users can now customise the `NWParameters` used to create new `NWConnection`s.	2025-04-16 14:33:56 +01:00
Rick Newton-Rogers	3d21b85af4	Enable Swift 6.1 jobs in CI (#232 ) Motivation: Swift 6.1 has been released, we should add it to our CI coverage. Modifications: Add additional Swift 6.1 jobs where appropriate in main.yml, pull_request.yml Result: Improved test coverage.	2025-04-14 10:52:43 +01:00
Gus Cairo	9eb2ebde13	Fix missing strict concurrency error (#231 ) Current strict concurrency checks don't work consistently in Xcode. This PR adds an additional flag (`-Xfrontend`) to our set of strict concurrency flags to make sure nothing has been missed when building. It also fixes an additional error uncovered after adding it.	2025-04-09 15:08:12 +01:00
Gus Cairo	92bb536b7e	Strict concurrency for NIOTransportServices and tests (#228 )	2025-04-02 10:54:00 +01:00
Rick Newton-Rogers	a9b23220e4	Enable macOS CI on pull requests (#229 ) Motivation: * Improve test coverage Modifications: Enable macOS CI to be run on pull request commits and make the use of the nightly runner pool for main.yml jobs explicit. Result: Improved test coverage.	2025-04-01 17:40:20 +01:00
Rick Newton-Rogers	a9da7c9aef	Enable macOS CI on merge to main and daily timer (#227 ) Enable macOS CI on merge to main and daily timer ### Motivation: * Improve test coverage * Check test pass/fail status * Monitor CI throughput ### Modifications: Enable macOS CI to be run on all merges to main and on a daily timer. ### Result: Improved test coverage run out-of-band at the moment so we can get a feeling for if any changes need to be made in the repo or in the CI pipelines to ensure timely and stable checks.	2025-03-26 17:01:32 +01:00
Johannes Weiss	862378ee24	test	2021-02-17 12:22:52 +00:00