Book Image

Hands-On MQTT Programming with Python

By : Gaston C. Hillar
Book Image

Hands-On MQTT Programming with Python

By: Gaston C. Hillar

Overview of this book

<p>MQTT is a lightweight messaging protocol for small sensors and mobile devices. This book explores the features of the latest versions of MQTT for IoT and M2M communications, how to use them with Python 3, and allow you to interact with sensors and actuators using Python.</p> <p>The book begins with the specific vocabulary of MQTT and its working modes, followed by installing a Mosquitto MQTT broker. You will use different utilities and diagrams to understand the most important concepts related to MQTT. You will learn to make all the necessary configuration to work with digital certificates for encrypting all data sent between the MQTT clients and the server. You will also work with the different Quality of Service levels and later analyze and compare their overheads.</p> <p>You will write Python 3.x code to control a vehicle with MQTT messages delivered through encrypted connections (TLS 1.2), and learn how leverage your knowledge of the MQTT protocol to build a solution based on requirements. Towards the end, you will write Python code to use the PubNub cloud-based real-time MQTT provider to monitor a surfing competition.</p> <p>In the end, you will have a solution that was built from scratch by analyzing the requirements and then write Python code that will run on water-proof IoT boards connected to multiple sensors in surfboards.</p>
Table of Contents (9 chapters)

Understanding callbacks

The previous code uses the recently installed paho-mqtt version 1.3.1 module to establish an encrypted connection with the MQTT server, subscribe to the vehicles/vehiclepi01/tests topic filter, and run code when we receive messages in the topic. We will use this code to understand the basics of paho-mqtt. The code is a very simple version of an MQTT client that subscribes to a topic filter and we will definitely improve it in the next sections.

The first line imports the variables we have declared in the previously coded config.py file. The second line imports paho.mqtt.client as mqtt. This way, whenever we use the mqtt alias, we will be referencing paho.mqtt.client.

When we declare a function, we pass this function as an argument to another function or method, or we assign this function to an attribute and then some code calls this function at some time...