java + multicast testing

McastReceiver.java

import java.net.*;

class McastReceiver {
  final static String DEFAULT_MCAST_GROUP = "224.56.78.90";
  final static int DEFAULT_MCAST_PORT = 12345;
  final static String JOIN_MSG = "hello!";

  MulticastSocket m_McastSock;
  InetAddress m_Addr;
  int m_Port;

  public McastReceiver() {
    this(DEFAULT_MCAST_GROUP, DEFAULT_MCAST_PORT);
  }

  public McastReceiver(String mcastGroup) {
    this(mcastGroup, DEFAULT_MCAST_PORT);
  }

  public McastReceiver(int port) {
    this(DEFAULT_MCAST_GROUP, port);
  }

  public McastReceiver(String mcastGroup, int port) {
    try {
      m_Addr = InetAddress.getByName(mcastGroup);
      m_Port = port;
      m_McastSock = new MulticastSocket(m_Port);
      m_McastSock.joinGroup(m_Addr);
    } catch (Exception e) {
      System.err.format("Could not create multicast socket: %s\n", e.getMessage());
      e.printStackTrace();
    }

    send(JOIN_MSG);
  }

  public void send(String msg) {
    try {
      DatagramPacket pkt = new DatagramPacket(msg.getBytes(), msg.length(), m_Addr, m_Port);
      m_McastSock.send(pkt);
      pkt = null;
    } catch (Exception e) {
      System.err.format("Could not construct and send packet: %s\n", e.getMessage());
      e.printStackTrace();
    }
  }

  public static void main(String[] argv) throws InterruptedException {
    McastReceiver m = new McastReceiver();
    while(true) {
      m.send("what's up?");
      Thread.sleep(3000);
    }
  }
}