code: def handler(self):
      
      self.pauseMovie()
      if tkMessageBox.askokcancel("Quit?", "Are you sure you want to quit?"):
        self.exitClient()
      else: # When the user presses cancel, resume playing.
        #self.playMovie()
        print "Playing Movie"
        threading.Thread(target=self.listenRtp).start()
        #self.playEvent = threading.Event()
        #self.playEvent.clear()
        self.sendRtspRequest(self.PLAY)
docs: Handler on explicitly closing the GUI window.