Stop the server.

def stop(self):
        """
        Stop the server.
        """
        log.debug("Stopping listeners")
        self.queue_lock.acquire()
        for s in self.listeners:
            log.debug("Stopping {}".format(s))
            s.shutdown()
            s.socket.close()
        self.cancel_queue()
        for t in self.threads:
            t.join()
        self.listeners = []
        self.threads = []
        self.is_running = False
        self.queue_lock.release()
        log.debug("Listeners stopped and threads joined")