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import java.net.*;

public final class MultiCastReceiver
     implements Runnable
{
    public static final int BUFFER_SIZE = 1500;

    private static volatile long messageCounter = 0L;
    private static long lastMessageCounter = 0L;
    private static long lastTimestamp = System.currentTimeMillis();

    public static void main(final String[] args)
        throws Exception
    {
        init(args);

        final int multiCastPort = 4447;
        final String address = args[0];
        final NetworkInterface networkInterface = NetworkInterface.getByName(args[1]);
        final MulticastSocket receiveSocket = new MulticastSocket(multiCastPort);
        final SocketAddress socketAddress = new InetSocketAddress(address, multiCastPort);

        receiveSocket.joinGroup(socketAddress, networkInterface);

        final byte[] buffer = new byte[BUFFER_SIZE];
        final DatagramPacket packet = new DatagramPacket(buffer, BUFFER_SIZE);

        new Thread(new MultiCastReceiver()).start();

        while (true)
        {
            packet.setLength(BUFFER_SIZE);
            receiveSocket.receive(packet);
            ++messageCounter;
        }
    }

    private static void init(final String[] args)
    {
        System.setProperty("java.net.preferIPv4Stack", "true");

        if (2 != args.length)
        {
            System.out.println("Usage: java MultiCastReceiver <multicast address> <interface name>");
            System.exit(1);
        }
    }

    public void run()
    {
        while (true)
        {
            try
            {
                Thread.sleep(1000L);
            }
            catch (InterruptedException ex)
            {
                break;
            }

            final long newTimestamp = System.currentTimeMillis();
            final long duration = newTimestamp - lastTimestamp;
            final long newMessageCounter = messageCounter;
            final long numberOfMessages = newMessageCounter - lastMessageCounter;

            System.out.format("Received %d messages in %dms\n",
                              Long.valueOf(numberOfMessages),
                              Long.valueOf(duration));

            lastTimestamp = newTimestamp;
            lastMessageCounter = newMessageCounter;
        }
    }
}