package test;

import java.net.DatagramPacket;

import java.net.InetAddress;

import java.net.MulticastSocket;

public class MulticastSender {

  private int port;

  private String host;

  private String data;

  public MulticastSender(String data, String host, int port) {

      this.data = data;

      this.host = host;

      this.port = port;

  }

  public void send() {

      try {

          InetAddress ip = InetAddress.getByName(this.host);

          DatagramPacket packet = new DatagramPacket(this.data.getBytes(),

                  this.data.length(), ip, this.port);

          MulticastSocket ms = new MulticastSocket();

          ms.send(packet);

          ms.close();

      } catch (Exception e) {

          e.printStackTrace();

      }

  }

  public static void main(String[] args) {

      int port = 1234;

      String host = "224.0.0.1";

      String data = "hello world.";

      MulticastSender ms = new MulticastSender(data, host, port);

      ms.send();

  }

}

2、Server端

package test;

import java.net.DatagramPacket;

import java.net.InetAddress;

import java.net.MulticastSocket;

public class MulticastListener {

  private int port;

  private String host;

  public MulticastListener(String host, int port) {

      this.host = host;

      this.port = port;

  }

  public void listen() {

      byte[] data = new byte[256];

      try {

          InetAddress ip = InetAddress.getByName(this.host);

          MulticastSocket ms = new MulticastSocket(this.port);

          ms.joinGroup(ip);

          DatagramPacket packet = new DatagramPacket(data, data.length);

          ms.receive(packet);

          String message = new String(packet.getData(), 0, packet.getLength());

          System.out.println(message);

          ms.close();

      } catch (Exception e) {

          e.printStackTrace();

      }

  }

  public static void main(String[] args) {

      int port = 1234;

      String host = "224.0.0.1";

      MulticastListener ml = new MulticastListener(host, port);

      while(true) {

          ml.listen();

      }

  }

}