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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();
}
}

}

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();
}

}