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
Table of Contents (16 chapters)
MQTT Essentials - A Lightweight IoT Protocol
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Debugging events in Swift

Now, we will take advantage of Xcode's debugging features to understand how methods are called when events occur.

Leave the application running on the simulator or the iOS device.

Open the source code for ViewController.swift.

Click on the left margin of the following line of code to establish a breakpoint at the first line of code in the mqtt method with didReceiveMessage as the external name of the second argument:

    print("Message received in topic (message.topic) with payload      (message.string!)")

Now, go to the iOS app and click or tap on the switch to turn on the motor again. After you change the value for the switch, the Node.js script will send a message with the new status for the motor and the mqtt method with didReceiveMessage as the external name of the second argument will be called. The Xcode debugger will hit the breakpoint we have set. The following screenshot shows the debugger hitting the breakpoint:

You can use all the features included in the...