Basic Mqtt test

README.md

** setup

1. Install python2
2. Install paho-mqtt libtray: pip install paho-mqtt
3. Download all three python files in the gist and store them in the same directory:
4. To run the subscriber run python mqtt_subscriber.py
5. To run the publisher run python mqtt_publisher.py

mqtt_client.py

from uuid import uuid4

from paho.mqtt.client import Client


class MqttClient(object):
	
	def __init__(self, client_id=None, host="iot.eclipse.org", port=1883):
		client_id = client_id or str(uuid4())
		self._client = Client(client_id=client_id)
		self.host = host
		self.port = port

	def connect(self):
		self._client.connect(host=self.host, port=self.port)
		print('established connection to client with host: {host}, port={port}'.format(host=self.host, port=self.port))

	def loop_forever(self):
		self._client.loop_forever()

	@property
	def client(self):
		return self._client

mqtt_publisher.py

import json
from time import sleep

from mqtt_client import MqttClient


class MqttPublisher(object):

	def __init__(self, topic):
		self.topic = topic
		self.mqtt = MqttClient()
		self.mqtt.connect()

	def publish_message(self, payload, qos=0, retain=False, serializer=json.dumps):
		print('publishing message: {message}'.format(message=payload))
		serialized_message = serializer(payload)
		self.mqtt.client.publish(topic=self.topic, payload=serialized_message, qos=qos, retain=retain)
		print('published message: {message} to topic: {topic}'.format(message=payload, topic=self.topic))


def publish_data():
	publisher = MqttPublisher(topic='voith/test')
	for i in range(10):
		data = dict({'lat': i, 'long': -i})
		publisher.publish_message(payload=data)
		sleep(1)

if __name__ == '__main__':
	publish_data()

mqtt_subscriber.py

import json

from mqtt_client import MqttClient


class MqttSubscriber(object):

	def __init__(self, topic, deserializer=json.loads):
		self.topic = topic
		self.deserializer = deserializer
		self.mqtt = MqttClient()
		self.mqtt.client.on_connect = self.on_connect
		self.mqtt.client.on_message = self.message_arrived

	def on_connect(self, client, userdata, flags, rc):
		print('connected to client with return code: {rc}'.format(rc=rc))
		client.subscribe(self.topic)

	def message_arrived(self, client, userdata, msg):
		# every time a message is published, this method will automatically be called
		print('received message: {msg} from topic: {topic}'.format(msg=msg.payload, topic=msg.topic))
		# this is how you decode the json.
		# the deserializer here points to json.dumps
		deserailized_data = self.deserializer(msg.payload)
		# this is how you access the lat and long
		# instead of the print put your lcd code here
		print('received latiude: {}'.format(deserailized_data['lat']))
		print('received longitude: {}'.format(deserailized_data['long']))

	def listen_for_messages(self):
		print('listening for messages from topic: {topic}'.format(topic=self.topic))
		self.mqtt.connect()
		# this is the event loop I was talking about..
		# think of this as a loop that runs forever.
		# whener a message is received it calls the on_message method 
		# which is pointing to message_arrived in our case.
		self.mqtt.loop_forever()


def start_subscriber():
	subscriber = MqttSubscriber(topic='voith/test')
	subscriber.listen_for_messages()

if __name__ == '__main__':
	start_subscriber()