Lightweight MQTT Library

Warning

The following mqtt library is still experimental: reconnections are not handled and some minor features are missing. Moreover it is not guaranteed to work on all supported devices.

This module contains an implementation of an MQTT client based on the paho-project embedded c client. It aims to be less memory consuming than the pure Python one.

The Client allows to connect to a broker (both via insecure and TLS channels) and start publishing messages/subscribing to topics with a simple interface.

Python callbacks can be easily set to handle incoming messages.

Client class

class Client(client_id, clean_session=False)
Parameters:
  • client_id – unique ID of the MQTT Client (multiple clients connecting to the same broken with the same ID are not allowed), can be an empty string with clean_session set to true.
  • clent_session – when True lets the broken assign a clean state to connecting client without remembering previous subscriptions or other configurations.

Instantiate the MQTT Client.

connect(host, keepalive, port=1883)
Parameters:
  • host – hostname or IP address of the remote broker.
  • port – network port of the server host to connect to, defaults to 1883.
  • keepalive – maximum period in seconds between communications with the broker. If no other messages are being exchanged, this controls the rate at which the client will send ping messages to the broker.
  • ssl_ctx

    optional ssl context (Zerynth SSL module) for secure mqtt channels.

    Connect to a remote broker and start the MQTT reception thread.

set_username_pw(username, password='')
Parameters:
  • username – connection username.
  • password – connection password.

Set connection username and password.

publish(topic, payload='', qos=0, retain=False)
Parameters:
  • topic – topic the message should be published on.
  • payload – actual message to send. If not given a zero length message will be used.
  • qos – is the quality of service level to use.
  • retain – if set to true, the message will be set as the “last known good”/retained message for the topic.

Publish a message on a topic.

This causes a message to be sent to the broker and subsequently from the broker to any clients subscribing to matching topics.

subscribe(topic, function, qos=0)
Parameters:
  • topic – topic to subscribe to.
  • function – callback to be executed when a message published on chosen topic is received.
  • qos – quality of service for the subscription.

Subscribe to a topic and set a callback for processing messages published on it.

The callback function is called passing two parameters: the MQTT client object and the payload of received message:

def my_callback(mqtt_client, payload):
    # do something with client and payload
    ...