def open(self):
        """
        Opens the port.
        
        :returns: Deferred that callbacks when we are ready to make and receive calls.
        """
        logging.debug("Opening rpc system")
        d = self._connectionpool.open(self._packet_received)
        
        def opened(_):
            logging.debug("RPC system is open")
            self._opened = True
            logging.debug("Starting ping loop")
            self._ping_loop.start(self._ping_interval, now=False)
        
        d.addCallback(opened)
        return d
Opens the port.
        
        :returns: Deferred that callbacks when we are ready to make and receive calls.