MQTT is a messaging protocol used for machine to machine communications in Internet of Things (IoT) Applications. It uses a Pub/sub architecture, with a central broker.
Within the space we have a MQTT broker running on Acidburn, where events like door openings, sensors, and the doorbell are currently broadcast on the hacman network.
Topics within MQTT are a series of levels, separated by forward slashes /. To subscribe to multiple topics at once, wildcards can be used. + matches a single level, and # matches anything below the current level.
Topic hierarchies can be set up however the user wants, we use it in the following way:
To install the mosquitto client
sudo apt-get install mosquitto-clients
To view the inner door being opened & closed, and by who
mosquitto_sub -h acidburn -t 'door/inner/#' -v
Note that # is used as a wildcard, and will match anything after the point it is posted. To view everything on the network:
mosquitto_sub -h acidburn -t '#' -v
First you'll need to install the python mqtt libraries:
sudo apt-get install python-mosquitto
Then the following code can be used to read messages on the MQTT network:
#!/usr/bin/python import mosquitto def on_message(mosq, obj, msg): if msg.topic == 'door/outer/opened/username': print("%s opened the outer door." % msg.payload) elif msg.topic == 'door/outer/buzzer': print('Buzzer') elif msg.topic == 'door/outer/invalidcard': print("Unknown card at outer door.") mqttc = mosquitto.Mosquitto("mqtt2bot") # The name of your client, probably should be unique mqttc.connect("acidburn") # the broker to connect to mqttc.subscribe("door/outer/#") # you can repeat this line multiple times to subscribe to additional topics mqttc.on_message = on_message # function to run when message is received while mqttc.loop() == 0: pass