NIOAsyncChannel server

server.swift

import NIOCore
import NIOHTTP1
import NIOPosix

/// Sendable server response that doesn't use ``IOData``
public typealias SendableHTTPServerResponsePart = HTTPPart<HTTPResponseHead, ByteBuffer>

/// Channel to convert HTTPServerResponsePart to the Sendable type HBHTTPServerResponsePart
final class HTTPSendableResponseChannelHandler: ChannelOutboundHandler, RemovableChannelHandler {
    typealias OutboundIn = SendableHTTPServerResponsePart
    typealias OutboundOut = HTTPServerResponsePart

    func write(context: ChannelHandlerContext, data: NIOAny, promise: EventLoopPromise<Void>?) {
        let part = unwrapOutboundIn(data)
        switch part {
        case .head(let head):
            context.write(self.wrapOutboundOut(.head(head)), promise: promise)
        case .body(let buffer):
            context.write(self.wrapOutboundOut(.body(.byteBuffer(buffer))), promise: promise)
        case .end:
            context.writeAndFlush(self.wrapOutboundOut(.end(nil)), promise: promise)
        }
    }
}

@available(macOS 14, *)
func server() async throws {
    let asyncChannel = try await ServerBootstrap(group: MultiThreadedEventLoopGroup.singleton)
        // Specify backlog and enable SO_REUSEADDR for the server itself
        .serverChannelOption(ChannelOptions.socketOption(.so_reuseaddr), value: 1)
        .childChannelOption(ChannelOptions.allowRemoteHalfClosure, value: true)
        .bind(host: "127.0.0.1", port: 8888, serverBackPressureStrategy: nil) { channel in
            return channel.eventLoop.makeCompletedFuture {
                try channel.pipeline.syncOperations.configureHTTPServerPipeline()
                try channel.pipeline.syncOperations.addHandler(HTTPSendableResponseChannelHandler())
                return try NIOAsyncChannel<HTTPServerRequestPart, SendableHTTPServerResponsePart>(
                    wrappingChannelSynchronously: channel,
                    configuration: .init()
                )
            }
        }
    print("Listening on 127.0.0.1:8888")
    await withDiscardingTaskGroup { group in
        do {
            try await asyncChannel.executeThenClose { inbound in
                for try await childChannel in inbound {
                    group.addTask {
                        try? await childChannel.executeThenClose { inbound, outbound in
                            for try await part in inbound {
                                if case .end = part {
                                    let buffer = ByteBuffer(string: "Hello world!\n")
                                    try await outbound.write(
                                        .head(
                                            .init(
                                                version: .http1_1,
                                                status: .ok,
                                                headers: ["Content-Length": "\(buffer.readableBytes)"]
                                            )
                                        )
                                    )
                                    try await outbound.write(.body(buffer))
                                    try await outbound.write(.end(nil))
                                    break
                                }
                            }
                        }
                    }
                }
            }
        } catch {
            print("ERROR: Waiting on child channel: \(error)")
        }
    }

}

if #available(macOS 14, *) {
    try await server()
}