Java MulticastSocket() Constructor

public MulticastSocket()    throws IOException

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
/*from   w  w w .  j a  va  2 s  . co m*/
public class Main {

  public static void main(String[] args) throws Exception {

    int port = 0;
    byte ttl = (byte) 1;

    InetAddress ia = InetAddress.getByName("127.0.0.1");

    byte[] data = "Here's some multicast data\r\n".getBytes();
    DatagramPacket dp = new DatagramPacket(data, data.length, ia, port);

    MulticastSocket ms = new MulticastSocket();
    ms.joinGroup(ia);
    for (int i = 1; i < 10; i++) {
      ms.send(dp, ttl);
    }
    ms.leaveGroup(ia);
    
    
    ia = ms.getInterface();
    System.out.println(ia);
    
    ms.close();
  }

}