SwiftNIO：发送和接收 UDP 广播

Question

我正在尝试使用 SwiftNIO 构建 TCP 服务器。服务器在网络中启动，但客户端不知道 IP 地址。因此，我也想启动一个 UDP 服务器，如果客户端出现，他会向网络发送一条广播消息。服务器将接收并回答，以便客户端现在知道 IP 地址。

是否可以使用 SwiftNIO 构建类似的东西？

Answer 1

是的，这也是可能的，SwiftNIO 中没有太多支持来简化此操作。 请参阅下面的注释示例，该示例将每秒向 en0 的广播地址和端口 37020 发送一次 HELLO WORLD。

import NIO

let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
defer {
    try! group.syncShutdownGracefully()
}

let matchingInterfaces = try System.enumerateInterfaces().filter {
    // find an IPv4 interface named en0 that has a broadcast address.
    $0.name == "en0" && $0.broadcastAddress != nil
}

guard let en0Interface = matchingInterfaces.first, let broadcastAddress = en0Interface.broadcastAddress else {
    print("ERROR: No suitable interface found. en0 matches \(matchingInterfaces)")
    exit(1)
}

// let's bind the server socket
let server = try! DatagramBootstrap(group: group)
    // enable broadast
    .channelOption(ChannelOptions.socket(SOL_SOCKET, SO_BROADCAST), value: 1)
    .bind(to: en0Interface.address)
    .wait()
print("bound to \(server.localAddress!)")

var buffer = server.allocator.buffer(capacity: 32)
buffer.writeString("HELLO WORLD!")

var destAddr = broadcastAddress
destAddr.port = 37020 // we're sending to port 37020

// now let's just send the buffer once a second.
group.next().scheduleRepeatedTask(initialDelay: .seconds(1),
                                  delay: .seconds(1),
                                  notifying: nil) { task in
    server.writeAndFlush(AddressedEnvelope(remoteAddress: destAddr,data: buffer)).map {
        print("message sent to \(destAddr)")
    }.whenFailure { error in
        print("ERROR: \(error)")
        // and stop if there's an error.
        task.cancel()
        server.close(promise: nil)
    }
}

try server.closeFuture.wait()

如果你想绑定到0.0.0.0 并发送到255.255.255.255，你可以使用这个

import NIO

let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
defer {
    try! group.syncShutdownGracefully()
}

// let's bind the server socket
let server = try! DatagramBootstrap(group: group)
    // enable broadast
    .channelOption(ChannelOptions.socket(SOL_SOCKET, SO_BROADCAST), value: 1)
    .bind(to: .init(ipAddress: "0.0.0.0", port: 0))
    .wait()
print("bound to \(server.localAddress!)")

var buffer = server.allocator.buffer(capacity: 32)
buffer.writeString("HELLO WORLD!")

// we're sending to port 37020
let destPort = 37020
let destAddress = try SocketAddress(ipAddress: "255.255.255.255", port: destPort)

// now let's just send the buffer once a second.
group.next().scheduleRepeatedTask(initialDelay: .seconds(1),
                                  delay: .seconds(1),
                                  notifying: nil) { task in
    server.writeAndFlush(AddressedEnvelope(remoteAddress: destAddress, data: buffer)).map {
        print("message sent to \(destAddress)")
    }.whenFailure { error in
        print("ERROR: \(error)")
        // and stop if there's an error.
        task.cancel()
        server.close(promise: nil)
    }
}
try server.closeFuture.wait()