Node.java

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.concurrent.CountDownLatch;

public abstract class Node {
	static final int PACKETSIZE = 65536;

	static DatagramSocket socket;
	Listener listener;
	CountDownLatch latch;

	Node() {
		latch = new CountDownLatch(1);
		listener = new Listener();
		listener.setDaemon(true);
		listener.start();
	}

	public abstract void onReceipt(DatagramPacket packet);

	/**
	 *
	 * Listener thread
	 * 
	 * Listens for incoming packets on a datagram socket and informs registered
	 * receivers about incoming packets.
	 */
	class Listener extends Thread {

		// Telling the listener that the socket has been initialized
		public void go() {
			latch.countDown();
		}

		public void run() { 		//Listen for incoming packets and inform receivers
			try 
			{
				latch.await();
				while (true) 		// Endless loop: attempt to receive packet, notify receivers, etc
				{
					DatagramPacket packet = new DatagramPacket(new byte[PACKETSIZE], PACKETSIZE);
					socket.receive(packet);

					onReceipt(packet);
				}
				
			} 
			catch (Exception e) 
			{
				if (!(e instanceof SocketException)) e.printStackTrace();
			}
		}
	}
}