Receiving from a Multicast Group
Once you've created a multicast socket and joined the group, all datagrams sent to its corresponding multicast address will be available to be read from the socket. You can read from the socket just like you would from a unicast socket. 

 public void read(
   MulticastSocket msocket, byte[] inbuf) {
     try {
        DatagramPacket packet = 
          new DatagramPacket(inbuf, inbuf.length);
 
        // Wait for packet
        msocket.receive(packet);
     
        // Data is now in inbuf
        int numBytesReceived = packet.getLength();
        } catch (IOException e) {
        }
 }