Book Image

MQTT Essentials - A Lightweight IoT Protocol

5 (1)
Book Image

MQTT Essentials - A Lightweight IoT Protocol

5 (1)

Overview of this book

This step-by-step guide will help you gain a deep understanding of the lightweight MQTT protocol. We’ll begin with the specific vocabulary of MQTT and its working modes, followed by installing a Mosquitto MQTT broker. Then, you will use best practices to secure the MQTT Mosquitto broker to ensure that only authorized clients are able to publish and receive messages. Once you have secured the broker with the appropriate configuration, you will develop a solution that controls a drone with Python. Further on, you will use Python on a Raspberry Pi 3 board to process commands and Python on Intel Boards (Joule, Edison and Galileo). You will then connect to the MQTT broker, subscribe to topics, send messages, and receive messages in Python. You will also develop a solution that interacts with sensors in Java by working with MQTT messages. Moving forward, you will work with an asynchronous API with callbacks to make the sensors interact with MQTT messages. Following the same process, you will develop an iOS app with Swift 3, build a website that uses WebSockets to connect to the MQTT broker, and control home automation devices with HTML5, JavaScript code, Node.js and MQTT messages

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Table of Contents (16 chapters)
MQTT Essentials - A Lightweight IoT Protocol
MQTT Essentials - A Lightweight IoT Protocol
Credits
Credits
About the Author
About the Author
Acknowledgment
Acknowledgment
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Customer Feedback
Customer Feedback
Dedication
Dedication
Preface
Preface
Free Chapter
1
Lightweight Messaging with MQTT 3.1.1 and Mosquitto
Lightweight Messaging with MQTT 3.1.1 and Mosquitto
Understanding convenient scenarios for the MQTT protocol
Working with the publish-subscribe pattern
Working with message filtering
Understanding the MQTT puzzle -- clients, servers, and connections
Installing a Mosquitto broker on Ubuntu Linux
Installing a Mosquitto broker on macOS
Installing a Mosquitto broker on Windows
Subscribing to topics
Publishing messages
Unsubscribing from topics
Working with best practices when creating topics
Understanding wildcards
Learning about the different Quality of Service levels
Working with at least once delivery
Working with exactly once delivery
Test your knowledge
Summary
2
Securing an MQTT Mosquitto Server
Securing an MQTT Mosquitto Server
Securing a Mosquitto server
Generating a private certificate authority to use TLS with Mosquitto
Creating a certificate for the Mosquitto server
Configuring TLS transport security in Mosquitto
Testing the MQTT TLS configuration with MQTT.fx
Testing the MQTT TLS configuration with MQTT-spy
Creating a certificate for each MQTT client
Configuring TLS client certificate authentication in Mosquitto
Testing the MQTT TLS client authentication with MQTT.fx
Testing the MQTT TLS configuration with MQTT-spy
Forcing the TLS protocol version
Test your knowledge
Summary
3
Controlling a Drone with Python
Controlling a Drone with Python
Understanding the requirements to control a drone with MQTT
Defining the topics and commands
Installing paho-mqtt for Python
Connecting the client to the MQTT server with Python
Understanding callbacks
Subscribing to topics with Python
Creating a class to represent a drone
Receiving messages with Python
Processing commands with Python
Sending messages with Python
Working with the network loop with Python
Test your knowledge
Summary
4
Interacting with Sensors in Java
Interacting with Sensors in Java
Understanding the requirements
Defining the topics and commands
Installing the Eclipse Paho Java Client
Creating a security helper class to establish a TLS secured connection
Configuring a TLS secured connection in Java
Working with asynchronous notifications and callbacks in Java
Subscribing to topics and understanding notification events in Java
Processing commands that interact with sensors in Java
Working with last will and testament in Java
Publishing messages with commands to target sensors
Test your knowledge
Summary
5
Controlling Home Automation in JavaScript
Controlling Home Automation in JavaScript
Understanding the requirements
Defining the topics and commands to control home automation
Enabling WebSockets for a Mosquitto server
Testing WebSockets with the Eclipse Paho client JavaScript utility
Understanding the Eclipse Paho JavaScript asynchronous client
Creating an HTML 5 web page to control LEDs
Publishing messages to target remote devices in JavaScript
Processing the received messages in JavaScript
Working with WebSockets to connect to the MQTT server
Subscribing to topics in JavaScript
Processing commands that interact with LEDs in Node.js
Running the home automation web application
Debugging asynchronous code with Chrome Developer Tools (CDT) in JavaScript
Securing MQTT over WebSockets with TLS
Test your knowledge
Summary
6
Interacting with Actuators in Swift
Interacting with Actuators in Swift
Understanding the requirements
Defining topics and commands
Enabling connections without TLS for a Mosquitto server
Installing the CocoaMQTT client library to create a new iOS app
Building the UI for the iOS app that will control an actuator
Understanding the CocoaMQTT client in Swift 3
Connecting to the MQTT server and subscribing to topics in Swift
Publishing messages to target actuators in Swift
Processing commands that interact with actuators in Node.js
Running the iOS app that controls an actuator with MQTT
Debugging events in Swift
Test your knowledge
Summary
Exersise Answers
Exersise Answers
Chapter 1, Lightweight Messaging with MQTT 3.1.1 and Mosquitto
Chapter 2, Securing an MQTT Mosquitto Server
Chapter 3, Controlling a Drone with Python
Chapter 4, Interacting with Sensors in Java
Chapter 5, Controlling Home Automation in JavaScript
Chapter 6, Interacting with Actuators in Swift

Understanding callbacks

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; this mechanism is known as callback. The name callback is used because the code calls back a function at some time.

The code declares three functions that we will specify as callbacks:

  • on_connect: This function will be called when the MQTT client receives a CONNACK response from the MQTT server, that is, when a connection has been successfully established with the MQTT server.

  • on_subscribe: This function will be called when the MQTT client receives a SUBACK response from the MQTT server, that is, when a subscription has been successfully completed.

  • on_message: This function will be called when the MQTT client receives a PUBLISH message from the MQTT server. Whenever the MQTT server publishes a message, based on the subscriptions for the client, this function will be called.

The...

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