Question

I try to receive datagram by multicast.
I try to use Java as below:

class looperThread extends Thread {
    public void run() {
        try {
            byte[] buffer = new byte[140];
            int port = 24680;
            String address = "224.0.0.10";
            try {
                socket = new MulticastSocket(port);
                InetAddress add = InetAddress.getByName(address);
                socket.joinGroup(add);
                while (true) {
                    try {
                        DatagramPacket packet = new DatagramPacket(buffer, buffer.length, add, port);
                        socket.receive(packet);
                        area.append("Received from " + packet.getAddress().toString() + "\n");
                    } catch (UnknownHostException ue) {
                    }
                }
            } catch (java.net.BindException b) {
            }
        } catch (IOException e) {
            System.err.println(e);
        }
    }
}

It works.
But I modify the code to Android as below.
Below on onCreate():

Thread mClockThread = new looperThread();
mClockThread.start();

class looperThread extends Thread {
    @Override
    public void run() {
        WifiManager wifi = (WifiManager) getSystemService(getApplicationContext().WIFI_SERVICE);
        MulticastLock mLock = wifi.createMulticastLock("mylock");
        mLock.acquire();
        try {
            byte[] buffer = new byte[140];
            int port = 24680;
            String address = "224.0.0.10";
            try {
                MulticastSocket socket = new MulticastSocket(port);
                InetAddress add = InetAddress.getByName(address);
                socket.joinGroup(add);
                while (true) {
                    try {
                        DatagramPacket packet = new DatagramPacket(buffer, buffer.length, add, port);
                        socket.receive(packet);
                        System.out.println("Received from " + packet.getAddress().toString() + "\n");
                    } catch (UnknownHostException ue) {
                    }
                }
            } catch (java.net.BindException b) {
            }
        } catch (IOException e) {
            System.err.println(e);
        }
    }
}

In fact, it send several datagrams.
But it only receive one or part of datagrams.
And in Java code, it receives all.
How should I do to improve?

Answer 1

I think it may cause by unstable wireless.
You should try to change a new AP to test.
It may your Android phone’s network interface controller conflict with the AP.