Question

我正在尝试进行SSDP发现广播，但无法从NWConnection.receive获取答复数据。

Network.framework相对较新，并且那里没有很多信息。我在这里想念什么？

SSDP发现广播已发送，UPnP设备已回复。（下面的Wireshark屏幕截图）

    import Foundation
    import Network

    let connection = NWConnection(host: "239.255.255.250", port: 1_900, using: .udp)

    func sendBroadcast() {
        let message = """
            M-SEARCH * HTTP/1.1
            ST: ssdp:all
            HOST: 239.255.255.250:1900
            MAN: ssdp:discover
            MX: 1
            """.data(using: .utf8)

        connection.send(content: message, completion: .contentProcessed { error in
                if let error = error {
                    print("Send Error: \(error)")
                } else {
                    print("Broadcast sent")
                }
            }
        )
    }

    connection.stateUpdateHandler = { newState in
        switch newState {
        case .setup:
            print("Connection: Setup")
        case .preparing:
             print("Connection: Preparing")
        case .waiting:
            print("Connection: Waiting")
        case .ready:
            print("Connection: Ready")
            sendBroadcast()
        case .failed:
            print("Connection: Failed")
        case .cancelled:
            print("Connection: Cancelled")
        }
    }

    connection.receive(minimumIncompleteLength: 2, maximumLength: 4_096) { data, context, isComplete, error in
        /// This is never executed
        ///
        print(data ?? "", context ?? "", isComplete, error ?? "")
    }

    connection.viabilityUpdateHandler = { update in
        print(update)
    }

    connection.betterPathUpdateHandler = { path in
        print(path)
    }

    connection.start(queue: .main)

    RunLoop.main.run()

Answer 1

结果证明 Network.framework 目前不支持 UDP广播（2019年2月） https://forums.developer.apple.com/message/316357#316357

Answer 2

使用UDP尝试以下方法：

connection.receiveMessage { (data, context, isComplete, error) in

    print(data ?? "", context ?? "", isComplete, error ?? "")
}

use here

中的一个很好的例子

我在TCP上遇到了相反的问题，并且正在使用connection.receiveMessage(...)，并且发生了相同的事情-从未输入回调。我在Apple Forums发表了一个问题。事实证明，TCP您只能使用：

connection.receive(minimumIncompleteLength: 1, maximumLength: 65535) { data, context, isComplete, error in
    
    print(data ?? "", context ?? "", isComplete, error ?? "")
}

Apple开发人员技术支持专家，名为eskimo answered it here：

。 TCP不是面向消息的协议，因此

receiveMessage(…)

没有任何意义。您想要的是

receive(minimumIncompleteLength:maximumLength:completion:)

话虽如此，请UDP试试connection.receiveMessage(…)

NWConnection SSDP发现未接收到数据

2 个答案: