Main entry point

After initializing our LED and client instances, we get to the program's main entry point.

We are registering a signal handler to capture Ctrl + C key combinations at line (19). The signal_handler method (not shown) simply turns off our LED and gracefully disconnects from the broker:

# Initialise Module
init_led()
init_mqtt()

if __name__ == "__main__":
    signal.signal(signal.SIGINT, signal_handler)    # (19)
    logger.info("Listening for messages on topic '" 
       + TOPIC + "'. Press Control + C to exit.")

    client.loop_start()                             # (20)
    signal.pause()

At line (20), the call to client.loop_start() is what allows our client to start, connect to the broker, and receive messages.