Java MulticastSocket(int port) Constructor

public MulticastSocket(int port)    throws IOException

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
//  w w  w. j a va  2s  . c  o  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(8080);
    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();
  }

}