Send message to recipient if the transport is running.

def maybe_sendraw(self, host_port: Tuple[int, int], messagedata: bytes):
        """ Send message to recipient if the transport is running. """

        # Don't sleep if timeout is zero, otherwise a context-switch is done
        # and the message is delayed, increasing its latency
        sleep_timeout = self.throttle_policy.consume(1)
        if sleep_timeout:
            gevent.sleep(sleep_timeout)

        # Check the udp socket is still available before trying to send the
        # message. There must be *no context-switches after this test*.
        if hasattr(self.server, 'socket'):
            self.server.sendto(
                messagedata,
                host_port,
            )