In this article, I explore MQTT (Message Queuing Telemetry Transport), a lightweight messaging protocol ideal for IoT applications like smart homes and sensors. Key features include a publish-subscribe architecture, minimal bandwidth usage, and support for Quality of Service levels, encryption, and persistent sessions. My journey involved using tools like Mosquitto, MQTTX, and Node.js. The article highlights why MQTT is crucial for real-time communication in IoT, its compatibility with various languages and platforms, and practical tips to start experimenting with this technology.

As part of my learning journey into IoT and real-time communication systems, I recently started working with MQTT (Message Queuing Telemetry Transport) — and here’s what I’ve learned so far.

What is MQTT? 🤔

MQTT is a lightweight, publish-subscribe messaging protocol designed for devices with limited resources and unreliable networks — which makes it perfect for IoT (Internet of Things) applications like smart homes, sensors, and remote monitoring systems.

It was originally developed by IBM and is now an open OASIS standard.

How MQTT Works – The Basics ⚙️

• Broker: The central server that receives and distributes messages. (Example: Mosquitto, HiveMQ, etc..)

• Publisher: Sends messages to a topic. Example: A temperature sensor publishing to home/room1/temperature.

• Subscriber: Listens to a topic and receives messages. Example: A mobile app that receives temperature updates..

It uses the TCP/IP stack, and the communication is asynchronous, which means it's fast and doesn’t block other processes.

Publish/Subscribe Model (vs HTTP) 🔄

With MQTT, you don’t ask for data like in HTTP — instead, you “subscribe” and get data as soon as it’s available

Is MQTT Secure? 🛡️

MQTT itself doesn’t enforce encryption or authentication, but you can add it using:

• TLS/SSL encryption for secure data transfer also supports WSS (Secure WebSocket connection with TLS encryption

• Username/Password for basic auth

• Token-based access (like JWT or OAuth)

Security depends on how you implement the broker and clients.

Tools I Used While Learning MQTT 📦

• Broker: Mosquitto (Open source, simple to set up locally)

• Client: MQTTX (GUI tool for testing)

• Platform: Node.js with mqtt npm package

• Cloud MQTT broker: HiveMQ Cloud (Free tier)

• Preferable in AWS IoT Core (Available for Free Tier Account)

Details Must Know

Some usefull features in MQTT are:

1. Publish/Subscribe Architecture

• Decouples producers (publishers) and consumers (subscribers).

• Clients do not communicate directly; instead, messages are sent via a broker.

2. Lightweight and Efficient

• Uses minimal bandwidth and system resources.

• Ideal for low-power devices, such as sensors and mobile apps.

3. Low Network Bandwidth Usage

• Header is only 2 bytes, making it perfect for limited connectivity environments.

4. Quality of Service (QoS) Levels

MQTT supports three levels of message delivery:

• QoS 0 – At most once (fire and forget)

• QoS 1 – At least once (might be duplicated)

• QoS 2 – Exactly once (guaranteed delivery)

5. Retained Messages

• The broker stores the last retained message on a topic and sends it immediately to new subscribers.

6. Last Will and Testament (LWT)

• If a client disconnects unexpectedly, the broker sends a predefined message (the “will”) to notify other clients.

7. Persistent Session Support

• Clients can retain session information across reconnects (e.g., subscriptions, undelivered messages).

8. Topic-Based Filtering

• Topics are hierarchical strings (e.g., home/kitchen/temp), and subscribers can use wildcards like + or #.

9. Security

• Supports TLS/SSL for encrypted communication.

• Can implement username/password authentication or certificates.

10. Platform and Language Support

• MQTT libraries are available in many languages (Python, JavaScript, C, Java, etc.) and work on almost all platforms.

And other notable features are Designed for devices that are always online, such as sensors, controllers, Helps detect dead connections quickly

My First Test App 🧪

I created a small Node.js script that simulates a temperature sensor publishing data every 5 seconds. Another client (my dashboard) subscribes to receive updates in real-time. This showed me how real-time data pipelines work in a production-like IoT system.

Why MQTT is Worth Learning in 2025 📝

• It’s super lightweight — perfect for embedded systems, mobile apps, and edge computing.

• It powers most IoT platforms like AWS IoT Core, Azure IoT Hub, and Google Cloud IoT.

• You can use it with Python, Node.js, C++, and even microcontrollers like ESP8266 or Raspberry Pi.

If you're exploring IoT development, sensor data streaming, or real-time alerts, MQTT is a must-know.

Final Tip 📌

Start by running Mosquitto locally and connect using MQTTX or a Node.js script. Once you’re confident, try deploying your own broker on a VPS or integrate it with cloud services.

Resource Used

WEFUZZ I have explored this resource to learn the above concepts