ios - Swift：在串口监视器上接收来自服务器的 UDP 数据包，但不在 ios 应用程序中

Question

我将 UDP 数据包发送到 wifi 模块并接收它们，我在串行端口监视器中成功监控它们，但无法在 iOS 应用程序中接收它们。

我正在使用网络框架进行连接和接收。连接部分工作得很好，但是当我为端口设置一个侦听器并尝试获取 rsponse 时，receiveMessage尽管我看到模块发送的输出包，但它并没有被调用。

class func connect()
{
    connection = NWConnection(host: hostUDP, port: portUDP, using: .udp)
    connection?.stateUpdateHandler =
    {
        (newState) in switch (newState)
        {
        case .ready:
            //The connection is established and ready to send and recieve data.
            print("ready")
            self.sendPaket(self.sendingPacket)
            self.receive()
        case .setup:
            //The connection has been initialized but not started
            print("setup")
        case .cancelled:
            //The connection has been cancelled
            print("cancelled")
        case .preparing:
            //The connection in the process of being established
            print("Preparing")
        default:
            //The connection has disconnected or encountered an error
            print("waiting or failed")
        }
    }
    connection?.start(queue: Protocols.sendQueue)
}

class func sendPaket(_ packet:String)
{
    let packet = dataWithHexString(hex: sendingPacket)
    print("converted version to byte is :\(packet)")
    connection?.send(content: packet, completion: NWConnection.SendCompletion.contentProcessed((
        {
            (NWError) in
            print("error in sending packet : \(String(describing:NWError))")
    })))

}

class func receive()
{
    connection?.receiveMessage(completion:
    {
        (data, context, isComplete, error) in
        print("Got it")
        if data != nil
        {
            print("context:\n")
            print((context?.protocolMetadata)!)
            Protocols.receivedPacket = data?.dataToHexEncodedString()
            print("received packet:\n")
            print(Protocols.receivedPacket!)
            let rec = Test()
            rec.label.text = Protocols.receivedPacket
        }
        print("receive error: \(String(describing: error))")
    })
}