package com.ericsson.tic.vi;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Timer;
import java.util.TimerTask;


/** 
 * KeepAlive periodically sends a message to the master system to
 * let it know that the VI is up and running and ready to recieve messages
 * from the master system. When the master system stops recieving messages,
 * it will stop sending data. This was added in order to cut out excess
 * traffic on the network.
 * 
 * @author Stefan Hellkvist
 */
public class KeepAlive extends TimerTask {
	static final int DELAY = 10000;
	private int serverPort, localPort;	
	InetAddress serverAddress;	
	
	public KeepAlive( int localPort, String serverAddress, int serverPort ) throws UnknownHostException {
		
		this.serverAddress = InetAddress.getByName(serverAddress);		
		this.serverPort = serverPort;
		this.localPort = localPort;		
		
		Timer t = new Timer( true );
		t.schedule( this, DELAY, DELAY );
		
	}

	
	public void run() {				
		try {
			
			DatagramSocket socket = new DatagramSocket();	
			byte[] buffer = ("HELLO " + localPort).getBytes();
			
			DatagramPacket packet = 
				new DatagramPacket( buffer, buffer.length, serverAddress, serverPort );
			
			socket.send(packet);
			
		} catch (SocketException e) {			
			e.printStackTrace();
		} catch (UnknownHostException e) {			
			e.printStackTrace();
		} catch (IOException e) {			
			e.printStackTrace();
		}				
	}	
}