To connect to a broker you only need to initialize the Flask-MQTT extension with your Flask application. You can do this by directly passing the Flask application object on object creation.
from flask import Flask from flask_mqtt import Mqtt app = Flask(__name__) mqtt = Mqtt(app)
The Flask-MQTT extension supports the factory pattern so you can instantiate
a Mqtt object without an app object. Use the init_app() function inside
the factory function for initialization.
from flask import Flask
from flask_mqtt import Mqtt
mqtt = Mqtt()
def create_app():
app = Flask(__name__)
mqtt.init_app(app)
The configuration of the MQTT client is done via configuration variables as it is common for Flask extension.
from flask import Flask from flask_mqtt import Mqtt app = Flask(__name__) app.config['MQTT_BROKER_URL'] = 'broker.hivemq.com' # use the free broker from HIVEMQ app.config['MQTT_BROKER_PORT'] = 1883 # default port for non-tls connection app.config['MQTT_USERNAME'] = '' # set the username here if you need authentication for the broker app.config['MQTT_PASSWORD'] = '' # set the password here if the broker demands authentication app.config['MQTT_KEEPALIVE'] = 5 # set the time interval for sending a ping to the broker to 5 seconds app.config['MQTT_TLS_ENABLED'] = False # set TLS to disabled for testing purposes mqtt = Mqtt()
All available configuration variables are listed in the configuration section.
To subscribe to a topic simply use :py:func:`flask_mqtt.Mqtt.subscribe`.
mqtt.subscribe('home/mytopic')
If you want to subscribe to a topic right from the start make sure to wait with the subscription until the client is connected to the broker. Use the :py:func:`flask_mqtt.Mqtt.on_connect` decorator for this.
@mqtt.on_connect()
def handle_connect(client, userdata, flags, rc):
mqtt.subscribe('home/mytopic')
To handle the subscribed messages you can define a handling function by using the :py:func:`flask_mqtt.Mqtt.on_message` decorator.
@mqtt.on_message()
def handle_mqtt_message(client, userdata, message):
data = dict(
topic=message.topic,
payload=message.payload.decode()
)
To unsubscribe use :py:func:`flask_mqtt.Mqtt.unsubscribe`.
mqtt.unsubscribe('home/mytopic')
Or if you want to unsubscribe all topics use :py:func:`flask_mqtt.Mqtt.unsubscribe_all`.
mqtt.unsubscribe_all()
Publishing a message is easy. Just use the :py:func:`flask_mqtt.Mqtt.publish` method here.
mqtt.publish('home/mytopic', 'hello world')
To enable logging there exists the :py:func:`flask_mqtt.Mqtt.on_log` decorator. The level variable gives the severity of the message and will be one of these:
.. tabularcolumns:: |p{6.5cm}|p{8.5cm}|
@mqtt.on_log()
def handle_logging(client, userdata, level, buf):
if level == MQTT_LOG_ERR:
print('Error: {}'.format(buf))
Flask-MQTT plays nicely with the Flask-SocketIO extension. Flask-SocketIO gives Flask applications access to low latency bi-directional communications between the clients and the server. So it is ideal for displaying live data, state changes or alarms that get in via MQTT. Have a look at the example to see Flask-MQTT and Flask-SocketIO play together. The example provides a small publish/subscribe client using Flask-SocketIO to insantly show subscribed messages and publish messages.
"""
A small Test application to show how to use Flask-MQTT.
"""
import eventlet
import json
from flask import Flask, render_template
from flask_mqtt import Mqtt
from flask_socketio import SocketIO
from flask_bootstrap import Bootstrap
eventlet.monkey_patch()
app = Flask(__name__)
app.config['SECRET'] = 'my secret key'
app.config['TEMPLATES_AUTO_RELOAD'] = True
app.config['MQTT_BROKER_URL'] = 'broker.hivemq.com'
app.config['MQTT_BROKER_PORT'] = 1883
app.config['MQTT_USERNAME'] = ''
app.config['MQTT_PASSWORD'] = ''
app.config['MQTT_KEEPALIVE'] = 5
app.config['MQTT_TLS_ENABLED'] = False
# Parameters for SSL enabled
# app.config['MQTT_BROKER_PORT'] = 8883
# app.config['MQTT_TLS_ENABLED'] = True
# app.config['MQTT_TLS_INSECURE'] = True
# app.config['MQTT_TLS_CA_CERTS'] = 'ca.crt'
mqtt = Mqtt(app)
socketio = SocketIO(app)
bootstrap = Bootstrap(app)
@app.route('/')
def index():
return render_template('index.html')
@socketio.on('publish')
def handle_publish(json_str):
data = json.loads(json_str)
mqtt.publish(data['topic'], data['message'])
@socketio.on('subscribe')
def handle_subscribe(json_str):
data = json.loads(json_str)
mqtt.subscribe(data['topic'])
@socketio.on('unsubscribe_all')
def handle_unsubscribe_all():
mqtt.unsubscribe_all()
@mqtt.on_message()
def handle_mqtt_message(client, userdata, message):
data = dict(
topic=message.topic,
payload=message.payload.decode()
)
socketio.emit('mqtt_message', data=data)
@mqtt.on_log()
def handle_logging(client, userdata, level, buf):
print(level, buf)
if __name__ == '__main__':
socketio.run(app, host='0.0.0.0', port=5000, use_reloader=False, debug=True)