问在多播套接字上接收单播

EN

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

public class MulticastReceiver {

        public static void main(String[] args) throws Exception {
            int mcPort = 1800;
            String mcIPStr = "239.255.255.250";
            MulticastSocket mcSocket = null;
            InetAddress mcIPAddress = null;
            mcIPAddress = InetAddress.getByName(mcIPStr);
            mcSocket = new MulticastSocket(mcPort);
            System.out.println("Multicast Receiver running at:"
                    + mcSocket.getLocalSocketAddress());
            mcSocket.joinGroup(mcIPAddress);


        boolean var=true;           
        while(var){ 
            DatagramPacket packet = new DatagramPacket(new byte[1024], 1024);
            System.out.println("Waiting for a  multicast message...");
            mcSocket.receive(packet);

        System.out.println("packet length is " +packet.getLength());


            String msg = new String(packet.getData(),0,1024);
            System.out.println("[Multicast  Receiver] Received:" + msg);
        }
            mcSocket.leaveGroup(mcIPAddress);
            mcSocket.close();


        }
    }