Book Image

Hands-On Mobile and Embedded Development with Qt 5

By : Lorn Potter
Book Image

Hands-On Mobile and Embedded Development with Qt 5

By: Lorn Potter

Overview of this book

Qt is a world-class framework, helping you to develop rich graphical user interfaces (GUIs) and multi-platform applications that run on all major desktop platforms and most mobile or embedded platforms. The framework helps you connect the dots across platforms and between online and physical experience. This book will help you leverage the fully-featured Qt framework and its modular cross-platform library classes and intuitive APIs to develop applications for mobile, IoT, and industrial embedded systems. Considerations such as screen size, device orientation changes, and small memory will be discussed. We will focus on various core aspects of embedded and mobile systems, such as connectivity, networking, and sensors; there is no IoT without sensors. You will learn how to quickly design a flexible, fast, and responsive UI that looks great. Going further, you will implement different elements in a matter of minutes and synchronize the UI elements with the 3D assets with high precision. You will learn how to create high-performance embedded systems with 3D/2D user interfaces, and deploy and test on your target hardware. The book will explore several new features, including Qt for WebAssembly. At the end of this book, you will learn about creating a full software stack for embedded Linux systems using Yocto and Boot to Qt for Device Creation.
Table of Contents (23 chapters)
Title Page
Dedication
About Packt
Foreword
Contributors
Preface
Index

QMqtt – Brokers of machine talk


MQTT is a publish-and-subscribe messaging transport. There was a similar framework in the Qt Mobility stack called Publish and Subscribe, which is now part of the officially unsupported QSystems API framework, which also includes QSystemInfo and QSystemFramework.

QMqtt is a framework for writing MQTT clients. You will need to install and run an MQTT broker, such as Mosquitto or HiveMQ, or use an internet-based service. For my development and testing purposes, I chose HiveMQ. You can download it from https://www.hivemq.com/.

They also have a public broker at http://www.mqtt-dashboard.com/index.html.

MQTT has a broker, or server that one or more clients connect to. The clients can then publish and/or subscribe to different topics.

You can use QWebSockets to access a broker, and there is an example in Qt, which uses the WebSocketIODevice class in the examples/mqtt/websocketsubscription directory.

QMqttClient

To start developing a QMqttClient, you will have to build...