/** 
 * This program is an example from the book "Internet 
 * programming with Java" by Svetlin Nakov. It is freeware. 
 * For more information: http://www.nakov.com/books/inetjava/ 
 */ 
import java.net.*; 
import java.io.IOException; 
 
public class MulticastListener { 
    public static final String 
        MULTICAST_GROUP_ADDRESS = "224.0.0.1"; 
    public static final int LISTENING_PORT = 2004; 
 
    public static final int MAX_PACKET_SIZE = 1024; 
 
    public static void main(String[] args) throws IOException { 
        MulticastSocket multicastSocket = 
            new MulticastSocket(LISTENING_PORT); 
        InetAddress multicastGroupAddr = 
            InetAddress.getByName(MULTICAST_GROUP_ADDRESS); 
        multicastSocket.joinGroup(multicastGroupAddr); 
        System.out.println("Joined to multicast group " + 
            MULTICAST_GROUP_ADDRESS + "."); 
 
        byte[] receiveBuf = new byte[MAX_PACKET_SIZE]; 
        DatagramPacket packet = 
            new DatagramPacket(receiveBuf, receiveBuf.length); 
        System.out.println("Listening for packets..."); 
        while (true) { 
            multicastSocket.receive(packet); 
            String packetAsString = new String( 
                packet.getData(), 0, packet.getLength()); 
            System.out.println("Received packet from " + 
                packet.getAddress().getHostAddress() + ":" + 
                packet.getPort() + " - " + packetAsString); 
        } 
    } 
}