Android 上非常简单的 UDP server/client 无法工作

Question

我正在尝试在 android 上做一个非常简单的客户端，以将 UDP 消息发送到 Android 上的服务器。

这是我的简单 UDP 客户端：

public class MyUDPClient {
    private static String TAG = "MyUDPClient";
    private DatagramSocket udpSocket;
    private InetAddress serverAddress;
    private int port;
    private Scanner scanner;

    public MyUDPClient(String destinationAddr, int port) throws SocketException, UnknownHostException {
        this.serverAddress = InetAddress.getByName(destinationAddr);
        this.port = port;
        udpSocket = new DatagramSocket(this.port);
        scanner = new Scanner(System.in);
    }

    public void send(String message) throws IOException {
        DatagramPacket p = new DatagramPacket(
                message.getBytes(), message.getBytes().length, serverAddress, port);
        Log.d(TAG, "udp client send: " + message + " to serverAddress " + serverAddress);
        this.udpSocket.send(p);
    }

    public void connect() {
        Log.d(TAG, "UDP connection to port " + port);
    }
}

这是我的简单 UDP 服务器：

public class MyUDPServer  {
    private String TAG = "MyUDPServer";
    private int port;
    private DatagramSocket udpSocket;
    OnMessageCallback onMessageCallback;

    public MyUDPServer(int port) throws SocketException {
        this.udpSocket = new DatagramSocket(port);
        this.port = port;
    }


    public interface OnMessageCallback {
        public void on(String message);
    }

    private void listen() throws Exception {
        Log.d(TAG, "listening UDP server on port " + port);
        String msg;

        while (true) {
            byte[] buf = new byte[256];
            DatagramPacket packet = new DatagramPacket(buf, buf.length);

            // blocks until a packet is received
            udpSocket.receive(packet);
            msg = new String(packet.getData()).trim();
            Log.d(TAG, "message received; " + msg);
            onMessageCallback.on(msg);
        }
    }

    public void start() throws Exception {
        listen();
    }

    public void setMessageCallback(OnMessageCallback onMessageCallback) {
        this.onMessageCallback = onMessageCallback;
    }

}

问题是服务器从未收到任何消息。我这样启动客户端：

MyUDPClient myUDPClient = new MyUDPClient("192.168.1.6", 8887);

因为它在模拟器上，我尝试过滤 IP 192.168.1.6，即使我调用 myUDPClient.send("message")，在 WireShark 上我什么也没有收到，这表明消息甚至没有离开计算机模拟器在哪里。

我做错了什么？

我在 Android 上创建了一个 WebSocket client/server，它运行良好。

我有这两个权限：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

Answer 1

在您的 MyUDPClient-class 中只需更改即可避免导致异常的“双重”绑定：

public MyUDPClient(String destinationAddr, int port) throws SocketException, UnknownHostException {
  super();
  this.serverAddress = InetAddress.getByName(destinationAddr);
  this.port = port;
  udpSocket = new DatagramSocket(this.port);
  scanner = new Scanner(System.in);
}

至

public MyUDPClient(String destinationAddr, int port) throws SocketException, UnknownHostException {
  super();
  this.serverAddress = InetAddress.getByName(destinationAddr);
  this.port = port;
  udpSocket = new DatagramSocket();
  //udpSocket = new DatagramSocket(this.port);
  scanner = new Scanner(System.in);
}

Answer 2

问题是我正在获取 NetworkOnMainThreadException 但它被记录到我没有过滤的 logcat 的另一部分。

从单独的线程执行 myudpClient.send("myMessage") 解决了问题。这就是为什么我什至看不到 Wireshark 上的输出，它甚至没有发送。

Android 上非常简单的 UDP server/client 无法工作

Very simple UDP server/client on Android wont work

java

networking

android

udp