private void start_ack_timer( ) {
     if (ackTimer == null)
       ackTimer = new Timer();
     ackTimer.schedule(new ackTime(), 1000);
   }

   private void stop_ack_timer() {
     if (ackTimer != null)
       ackTimer.cancel();
     ackTimer = null;
   }

   class ackTime extends TimerTask {
     public void run() {
       System.out.println("Ack Timed out!");
       swe.generate_acktimeout_event();
       this.cancel(); //Terminate the timer thread
     }
   }