This book is aimed at Python developers who want to develop applications that can interact with other applications and devices, such as IoT boards, sensors, and actuators.

Chapter 1, Installing an MQTT 3.1.1 Mosquitto Server, starts our journey toward the usage of the preferred IoT publish-subscribe lightweight messaging protocol in diverse IoT solutions, combined with mobile apps and web applications. We will learn how MQTT and its lightweight messaging system work. We will understand the MQTT puzzle: clients, servers (formerly known as brokers), and connections. We will learn the procedures to install an MQTT 3.1.1 Mosquitto server in Linux, macOS, and Windows. We will learn special considerations for running a Mosquitto server on the Cloud (Azure, AWS, and other cloud providers).

Chapter 2, Using Command-Line and GUI Tools to Learn How MQTT Works, teaches us to work with command-line and GUI tools to learn how MQTT works in detail. We will learn MQTT basics, the specific vocabulary for MQTT, and its working modes. We will use different utilities and diagrams to understand the most important concepts related to MQTT. We will understand everything we need to know before writing Python code to work with the MQTT protocol. We will work with the different Quality of Service levels, and we will analyze and compare their overheads.

Chapter 3, Securing an MQTT 3.1.1 Mosquitto Server, focuses on how to secure an MQTT 3.1.1 Mosquitto server. We will make all the necessary configurations to work with digital certificates to encrypt all the data sent between the MQTT clients and the server. We will use TLS, and we will learn to work with client certificates for each MQTT client. We will also learn to force the desired TLS protocol version.

Chapter 4, Writing Code to Control a Vehicle with Python and MQTT Messages, focuses on writing Python 3.x code to control a vehicle with MQTT messages delivered through encrypted connections (TLS 1.2). We will write code that will be able to run on different popular IoT platforms, such as a Raspberry Pi 3 board. We will understand how we can leverage our knowledge of the MQTT protocol to build a solution based on requirements. We will learn to work with the latest version of the Eclipse Paho MQTT Python client library.

Chapter 5, Testing and Improving Our Vehicle Control Solution in Python, outlines using our vehicle control solution with MQTT messages and Python code. We will learn how to process commands received in MQTT messages with Python code. We will write Python code to compose and send MQTT messages with commands. We will work with the blocking and threaded network loops, and we will understand the difference between them. Finally, we will take advantage of the last will and testament feature.

Chapter 6, Monitoring a Surfing Competition with Cloud-Based Real-Time MQTT Providers and Python, gets you started with writing Python code to use the PubNub cloud-based, real-time MQTT provider in combination with a Mosquitto MQTT server to monitor a surfing competition. We will build a solution from scratch by analyzing the requirements, and we will write Python code that will run on waterproof IoT boards connected to multiple sensors in surfboards. We will define the topics and commands, and we will work with a cloud-based MQTT server, in combination with the Mosquitto MQTT server used in the previous chapters.

Appendix, Solutions, the right answers for the Test Your Knowledge sections of each chapter are included in the appendix.

You need a basic knowledge of Python 3.6.x and IoT boards.

@staticmethod
    def on_subscribe(client, userdata, mid, granted_qos):
        print("I've subscribed with QoS: {}".format(
            granted_qos[0]))

 time.sleep(0.5) 
       client.disconnect() 
       client.loop_stop()

 sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa

Feedback from our readers is always welcome.

General feedback: Email [email protected] and mention the book title in the subject of your message. If you have questions about any aspect of this book, please email us at [email protected].

Errata: Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you have found a mistake in this book, we would be grateful if you would report this to us. Please visit www.packtpub.com/submit-errata, selecting your book, clicking on the Errata Submission Form link, and entering the details.

Piracy: If you come across any illegal copies of our works in any form on the Internet, we would be grateful if you would provide us with the location address or website name. Please contact us at [email protected] with a link to the material.

If you are interested in becoming an author: If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, please visit authors.packtpub.com.