Stop server and all its threads.

def stop(self):
        """
        Stop server and all its threads.
        """
        try:
            self.running = False
            logger.info('Waiting tasks to finish...')
            self.queue.join()
            self.socket.close()
            logger.info('Exiting (C-Ctrl again to force it)...')
        except KeyboardInterrupt:
            logger.info('Forced.')
            sys.exit(1)