fix calback registration

    def send(self,stage):

        self.socket.send("%d %d" % (self.topic, self.stage_map[stage]))

    def __init__(self,addr="localhos:5556"):

    def __init__(self,addr="localhost:5556"):

        context = zmq.Context()

        self.socket = context.socket(zmq.PUB)

        self.socket.bind("tcp://%s" % addr)

if __name__ == "__main__":

    parser = argparse.ArgumentParser(description='')

    parser.add_argument('addr', type=str, default="localhos:5556", nargs="?")

    parser.add_argument('addr', type=str, default="localhost:5556", nargs="?")

    args = parser.parse_args()

    conn = krpc.connect()

    control = vessel.control

    rocket = ModelRocket(args.addr)

    stage = conn.add_stream(getattr, control.current_stage, 'stage')

    stage = conn.add_stream(getattr, control, 'current_stage')

    stage.add_callback(rocket.send)

    stage.start()