d. Based on Example1Sender.java, create a program Example1SenderReceiver.java which joins the multicast group, sends a message, then listens for (receives) a multicast message before closing the multicast socket and exiting. Compile the program, then start two or more Receiver processes before starting the SenderReceiver process. Describe the outcome. Turn in the listing of SenderReceiver.java.

Question

This exercise is based on Example1 presented in this chapter



Both processes receive the message sent by the SenderReceiver – a process which has joined a multicast group receives the messages that it itself sends.

Answer 1

```
try {
// create the multicast socket
group = InetAddress.getByName("239.1.2.3");
s = new MulticastSocket(3456);

s.joinGroup(group);

s.setTimeToLive(32); // restrict multicast to processes
// running on hosts at the same site.
String msg = args[0];
DatagramPacket packet =
new DatagramPacket(msg.getBytes(), msg.length(),
group, 3456);
s.send(packet);
System.out.println("Waiting to receive");
byte[] buf = new byte[100];
// code added to receive a packet
DatagramPacket recv = new DatagramPacket(buf, buf.length);
s.receive(recv);
System.out.println(new String(buf));

s.close();
}
catch (Exception ex) { // here if an error has occurred
System.out.println("Problem: " + ex);
}

```