MQTT – WHAT IS IT?

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“MQTT is the quiet connector, enabling intelligent devices to speak fluently in real time, even when bandwidth is low and power is precious.” – MJ Martin

WHAT IS MQTT?

MQTT stands for Message Queuing Telemetry Transport.

It’s a lightweight messaging protocol often used in IoT (Internet of Things) applications to connect devices and sensors over a network. MQTT is designed to be simple, efficient, and reliable, making it ideal for situations where network bandwidth and battery power are limited.

WHY IS MQTT USEFUL?

MQTT is highly useful, especially in IoT and other data-driven applications, because it is designed for efficiency, reliability, and simplicity in communication. Here’s why MQTT is particularly beneficial:

1. Low Bandwidth Consumption

• MQTT is lightweight, with minimal overhead, which makes it ideal for networks with limited bandwidth or devices with low processing power. This is crucial for IoT devices that rely on mobile networks or constrained connectivity.

2. Optimized for Low Power Devices

• Many IoT devices operate on battery power, making efficient energy use essential. MQTT’s low overhead and ability to maintain connections with minimal energy usage help extend battery life for these devices.

3. Reliable and Real-Time Messaging

• MQTT provides Quality of Service (QoS) levels, allowing users to choose how reliable the message delivery should be, from “best effort” to “guaranteed delivery.” This flexibility allows MQTT to support both non-critical and mission-critical applications.

4. Publish/Subscribe Model for Scalability

• With a publish/subscribe model, MQTT easily scales to connect thousands of devices to a single broker. It allows multiple devices to communicate without needing direct connections, which reduces the network complexity and overhead.

5. Persistent Connections

• MQTT maintains a persistent connection between the client and broker, enabling devices to stay connected and exchange data with minimal delay. This is key for applications requiring real-time monitoring, like environmental sensors or location tracking.

6. Efficient Handling of Data with Topics

• MQTT uses topics to structure data efficiently. For example, if sensors in multiple rooms publish to distinct topics, only subscribers interested in specific rooms will receive relevant data, reducing data clutter and making it easier to handle large volumes of messages.

7. Supports Offline and Intermittent Connectivity

• MQTT is built to handle intermittent network connectivity, allowing devices to reconnect and resume data transfer without much complexity. For instance, the Last Will and Testament feature can notify others if a device unexpectedly disconnects, improving network resilience.

8. Flexible for Diverse Use Cases

• Because of its simplicity, MQTT is adaptable to many types of IoT systems: from home automation (smart lights, thermostats) to industrial automation (machine sensors, remote monitoring), healthcare (wearable devices), and beyond.

Example Use Cases of MQTT

• Smart Homes: Connecting devices like lights, thermostats, and security cameras, allowing real-time control and monitoring.
• Industrial IoT: Connecting machinery, sensors, and control systems in factories for efficient monitoring and predictive maintenance.
• Healthcare Devices: Monitoring health data from wearables in real time, such as heart rate or glucose levels.
• Transportation and Fleet Tracking: Tracking vehicles and assets in real-time with minimal data use.

Overall, MQTT’s ability to handle real-time data exchange reliably and efficiently makes it indispensable in scenarios where connectivity, battery life, and scalability are essential.

HOW DOES MQTT WORK?

MQTT operates on a simple publish/subscribe messaging model, which is ideal for efficient, low-bandwidth communication between devices. Here’s a breakdown of how it works:

1. Broker-Centric Architecture

• MQTT relies on a central server called a broker, which manages all message distribution.
• Devices (called clients) don’t communicate directly; instead, they publish and subscribe to topics through the broker.

2. Publish/Subscribe Model

• Publishers send messages to specific topics on the broker.
• Subscribers express interest in certain topics to receive messages from those topics.
• For example, a temperature sensor might publish data to a topic called home/livingroom/temperature, and any device subscribed to this topic will receive the temperature data.

3. Topics and Message Filtering

• Topics are organized hierarchically, resembling folder paths, which makes it easy to filter messages. For example, home/kitchen/temperature and home/livingroom/temperature are distinct topics.
• Subscribers can use wildcards (like home/#) to receive all messages under a specific hierarchy.

4. Quality of Service (QoS) Levels

• MQTT has three QoS levels to control message delivery:
  • QoS 0: “At most once” – Messages are sent once, without acknowledgment. There’s no guarantee of delivery.
  • QoS 1: “At least once” – Messages are guaranteed to be delivered at least once, with acknowledgment.
  • QoS 2: “Exactly once” – Messages are guaranteed to be delivered only once, ensuring no duplicates.

5. Retained Messages and Last Will

• Retained messages allow the broker to store the last message sent to a topic, which is sent immediately to new subscribers.
• Last Will and Testament (LWT) messages are defined by clients to notify other devices if they disconnect unexpectedly, which is useful in monitoring device status.

6. Lightweight and Efficient

• MQTT’s simplicity and minimal packet overhead make it highly suitable for low-power devices with limited resources, like IoT sensors.

Example of Workflow

1. A sensor publishes temperature data to home/livingroom/temperature.
2. The broker receives this data and checks if there are any subscribers to this topic.
3. Devices that have subscribed to home/livingroom/temperature receive the temperature data immediately.

This setup makes MQTT very efficient for real-time communication in IoT networks, home automation, and other scenarios where devices need to interact frequently.

CAN MQTT BE USED IN OTHER WAYS?

MQTT can be used in many creative and varied applications beyond traditional IoT. For instance, it’s useful in managing large-scale data in smart city infrastructure, such as monitoring traffic lights, air quality, and street lighting. In the financial sector, MQTT is used for real-time data feeds, enabling stock prices or transaction updates to be distributed reliably and instantly to numerous clients. Additionally, MQTT supports remote collaboration and real-time communication for team collaboration tools by ensuring message delivery with low latency. The gaming industry also leverages MQTT for real-time multiplayer synchronization, enabling quick updates on game states between players. Beyond this, MQTT is applied in agriculture for smart farming, where environmental data like soil moisture and temperature are monitored to optimize crop yield and resource usage. Given its flexibility, MQTT continues to be adopted in fields that require reliable, real-time data exchange across distributed devices.

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About the Author:

Michael Martin is the Vice President of Technology with Metercor Inc., a Smart Meter, IoT, and Smart City systems integrator based in Canada. He has more than 40 years of experience in systems design for applications that use broadband networks, optical fibre, wireless, and digital communications technologies. He is a business and technology consultant. He was a senior executive consultant for 15 years with IBM, where he worked in the GBS Global Center of Competency for Energy and Utilities and the GTS Global Center of Excellence for Energy and Utilities. He is a founding partner and President of MICAN Communications and before that was President of Comlink Systems Limited and Ensat Broadcast Services, Inc., both divisions of Cygnal Technologies Corporation (CYN: TSX). Martin served on the Board of Directors for TeraGo Inc (TGO: TSX) and on the Board of Directors for Avante Logixx Inc. (XX: TSX.V).  He has served as a Member, SCC ISO-IEC JTC 1/SC-41 – Internet of Things and related technologies, ISO – International Organization for Standardization, and as a member of the NIST SP 500-325 Fog Computing Conceptual Model, National Institute of Standards and Technology. He served on the Board of Governors of the University of Ontario Institute of Technology (UOIT) [now OntarioTech University] and on the Board of Advisers of five different Colleges in Ontario.  For 16 years he served on the Board of the Society of Motion Picture and Television Engineers (SMPTE), Toronto Section.  He holds three master’s degrees, in business (MBA), communication (MA), and education (MEd). As well, he has three undergraduate diplomas and five certifications in business, computer programming, internetworking, project management, media, photography, and communication technology. He has completed over 30 next generation MOOC continuous education in IoT, Cloud, AI and Cognitive systems, Blockchain, Agile, Big Data, Design Thinking, Security, Indigenous Canada awareness, and more.