Using Python and MQTT on a Rasberry Pi

 Mosquitto (mosquitto.org) is an open source message broker that implements the MQ Telemetry Transport protocol. MQTT (mqtt.org) privides a lightweight method of carrying out messaging using a publish/subscribe model. More about the MQTT protocol you can read at http://mosquitto.org/man/mqtt-7.html


After installing mosquitto 1.0.5 on my rasberry pi  I wrote the following two python scripts to experiment myself.

The code is shown below and it is self explanatory:

mosqsrv.py

#!/usr/bin/python

import mosquitto

#define what happens after connection
def on_connect (mosq, obj, rc):
        if rc==0:
                print "connected"

#On receipt of a message create a message
def on_message(mosq, obj, msg):
        print msg.topic+', '+msg.payload

#create a roker
mqttc = mosquitto.Mosquitto("python_sub")

#define the callbacks
mqttc.on_connect = on_connect
mqttc.on_message = on_message

#connect
mqttc.connect("localhost", 1883, 60)

#subscribe to topic test
mqttc.subscribe("test", 0)

#keep connected to broker
while mqttc.loop()==0:
        pass

mosqcl.py

#!/usr/bin/python

import mosquitto

#define what happens after connection
def on_connect (mosq, obj, rc):
        print("connected")

#create a broker
mqttc = mosquitto.Mosquitto("python_test")

#connect
mqttc.connect("192.168.1.105",1883, 60)

#publish to broker
mqttc.publish("test", "hello world!", 1)

mqttc.disconnect()

To test it I run mosquitto broker from the command line after editing the mosquitto.conf file to define the run user.