earth.py

# Program to see if there is a live connection with heaven
import sys
import time
from datetime import datetime

import zmq
from zmq.eventloop.ioloop import IOLoop, PeriodicCallback
from zmq.eventloop.zmqstream import ZMQStream
context = zmq.Context()

import infoPack_pb2

# Set up publisher connection to send messages to the sendBroker
publisher = context.socket(zmq.PUB)
publisher.bind('tcp://*:12345')

# Set up subscriber connection to receive the heartbeats back
subscriber = context.socket(zmq.SUB)
subscriber.connect('tcp://localhost:54321')
subscriber.setsockopt(zmq.SUBSCRIBE, '')

loop = IOLoop.instance()
timeout = None
subscriber = ZMQStream(subscriber, loop)

handshake = False
print('\nWait for handshake from heaven')

def beat():
    """Send a heart beat"""
    global handshake
    beat = infoPack_pb2.heartBeat()
    beat.heartBeat = 1
    beatPb = beat.SerializeToString()
    publisher.send(beatPb)
    if handshake != False:
        sys.stdout.write('.')
        sys.stdout.flush()

def handleSilence():
    """Call this function is no messages have been received in a while"""
    if handshake != False: print('Heaven is silent')
    resetTimeout()

def resetTimeout():
    """Reset the timeout when no messages have been received"""
    global timeout
    if timeout: loop.remove_timeout(timeout)
    timeout = loop.add_timeout(time.time() + 2, handleSilence)

def handleHeartBeat(message):
    """If a heartBeat has been received from hemel the timeout should be reset"""
    beat = infoPack_pb2.heartBeat()
    beat.ParseFromString(message)
    if beat.heartBeat == 1:
        global handshake
        if handshake == False:
            handshake = True
            print('Handshake received from heaven')
        resetTimeout()

# Send heart beat every second
sendHeartBeats = PeriodicCallback(beat, 1000, loop)
sendHeartBeats.start()
# Start inital 'no messages' timeout
resetTimeout()
# Set handler for received heartbeats
subscriber.on_recv(handleHeartBeat)
# Start event loop
loop.start()