MQTT - Topics, QoS, and LWT

Relevance

IoT is no longer just a trend; it is a necessity for businesses, industries, and even individual users. From building automation to remote monitoring systems and intelligent sensor networks, connectivity is shaping the future of technology.

The challenge? Finding efficient, scalable, and secure solutions to ensure that IoT growth is sustainable and manageable. MQTT and other optimized protocols play a fundamental role in this scenario.

The Internet of Things (IoT) is revolutionizing the way devices, machines, and people interact. In a world where connectivity is increasingly demanded and resources (bandwidth, energy, hardware) are limited, efficient and scalable solutions like MQTT are becoming the backbone of the IoT industry.

Why is IoT becoming dominant?

1️. Exponential growth of connected devices: It is estimated that by 2030, there will be over 25 billion IoT devices in operation.

2️. Resource optimization: Lightweight protocols like MQTT enable efficient communication even over unstable networks or with low bandwidth.

3️. Development of Smart Cities and Industry 4.0: Automated systems for environmental monitoring, intelligent transportation, and industrial production are already a reality.

4️. Increasing demand for automation and data analytics: IoT is at the core of artificial intelligence and machine learning, improving decision-making processes and optimizing resource consumption.

5️. Transition towards sustainable solutions: IoT helps reduce energy waste, improve resource management, and optimize production processes.

Abstract

MQTT (Message Queuing Telemetry Transport) is a lightweight, efficient protocol designed specifically for resource-constrained devices and unreliable networks, prevalent in the IoT (Internet of Things) ecosystem. This course covers MQTT’s fundamental concepts, including its publish/subscribe architecture, detailed message types, and critical message properties such as Quality of Service (QoS)and the Last Will and Testament (LWT).

MQTT plays a crucial role in smart home and building automation due to its inherent advantages, such as minimal bandwidth usage, scalability, reliability, and real-time communication capabilities.

Part 03 - MQTT Topics, QoS, and LWT

This module provides an in-depth exploration of advanced MQTT protocol features, focusing on how to design scalable and resilient messaging structures in real-world IoT and automation systems.

It begins with a comprehensive explanation of MQTT topics and wildcards, including their syntax, best practices, and performance considerations. Learners will understand how topics are structured hierarchically and how wildcard characters (+, #) enable flexible and efficient subscriptions. Specific attention is given to optimizing topic filters to prevent network overload and enhance broker performance.

The second section focuses on Quality of Service (QoS) levels, explaining the message delivery guarantees of QoS 0 (best effort), QoS 1 (at least once), and QoS 2 (exactly once). Learners will analyze how QoS impacts bandwidth, latency, duplication handling, and system reliability. Best practices and downgrade rules between publisher and subscriber are thoroughly addressed.

The final section introduces the Last Will and Testament (LWT) mechanism, a key MQTT feature that allows clients to notify others in the event of an unexpected disconnection. Through use cases from smart homes, fleet management, and critical monitoring systems, learners will understand how LWT and retained messages can work together to build resilient networks.

Overall, this module equips learners with practical skills to configure MQTT networks with high efficiency, fault tolerance, and real-time responsiveness.