Android收不到组播包

Question

我正在研究多播套接字。我编写了一个向 android 客户端发送消息的服务器。到目前为止，客户端应该只记录收到的消息。我注意到我的设备没有收到多播数据包。

这是服务器的代码(在电脑上运行):

public class MulticastServer{

private int port;

private boolean running = false;

private MulticastSocket serverSocket;

private InetAddress group;

private String multicastAddress = "230.192.0.11";

public MulticastServer(int port) {
    super();
    this.port = port;
    init();
}

public MusicStreamerServer() {
    this(5500);
}

private void init() {

    try {
        group = InetAddress.getByName(multicastAddress);
        serverSocket = new MulticastSocket(port);
        serverSocket.joinGroup(group);
    } catch (IOException e) {
        e.printStackTrace();
    }

}

public void start() throws IOException {
    System.out.println("server started");

    if (running)
        return;

    running = true;

    new Thread(new Runnable() {

        @Override
        public void run() {

            byte[] buf = new byte[1024];

            DatagramPacket packet = new DatagramPacket(buf, buf.length,
                    group, port);

            String msg = "msg";


            while (running) {

                                    packet.setData(msg.getBytes(), 0, msg.length());


                try {
                    serverSocket.send(packet);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        }
    }).start();

}

public void stop() throws IOException {
    running = false;
} }

这是安卓客户端的代码:

public class MainActivity extends Activity {

private MulticastSocket socket;

private InetAddress group;

private String multicastAddress = "230.192.0.11";

private int port = 5500;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    init();
}

private void init() {

    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
            .permitAll().build();

    StrictMode.setThreadPolicy(policy);

    try {
        group = InetAddress.getByName(multicastAddress);
        socket = new MulticastSocket(port);
        socket.joinGroup(group);
        socket.setBroadcast(true);
    } catch (IOException e) {
        e.printStackTrace();
        Log.wtf("init", e.getMessage());
    }

    new Thread(new Runnable() {

        @Override
        public void run() {

            WifiManager wm = (WifiManager) getSystemService(Context.WIFI_SERVICE);
            WifiManager.MulticastLock multicastLock = wm
                    .createMulticastLock("mylock");

            multicastLock.acquire();

            byte[] buf = new byte[1024];

            while (true) {

                try {
                    socket.receive(packet);

                    Log.d("receiver","received = " + (new String(packet.getData())));

                } catch (IOException e) {
                    e.printStackTrace();
                }

            }

        }
    }).start();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}}

我用 2 种不同的设备测试了代码。 Nexus4 和 Nexus7 (2013) 均运行最新的 Android。

谁能帮帮我？

谢谢

Answer 1

我看到这个问题确实不一致。

安卓版本:4.2.x

在三星 S4 上:多播按预期工作。

在三星 Note 10.1 和 Nexus 4.2.3 上多播未按预期工作。

239.x.x.x 不受支持(遗憾的是它是用于多播电视的那个......)224.0.0.251 按预期工作。

我认为他们的面具有问题。

多播地址通常是|1 1 1 0|多播地址 | 224.0.0.0 - 239.255.255.255

  11100000.00000000.00000000.00000001 = 224.0.0.1
  11101111.00000000.00000000.00000001 = 239.0.0.1

所以掩码应该是 224.0.0.0/4 而不是 224.0.0.0/8