What is MQTT? A simple explanation for IoT beginners
MQTT is the lightweight messaging protocol at the heart of IoT. Learn how it works — broker, topics, publish/subscribe and QoS — through easy examples.
If you’re new to IoT, you’ll almost certainly run into MQTT. It’s the most widely used messaging protocol for connected devices, from tiny greenhouse sensors to factory monitoring systems. This article explains MQTT as simply as possible.
What is MQTT?
MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol built on the publish/subscribe model. It’s designed for resource-constrained devices and unreliable networks — exactly the IoT reality.
Instead of devices calling each other directly, every message flows through a central “post office” called a broker.
Three core concepts
- Broker — the intermediary server that receives and distributes messages. Examples: EMQX, HiveMQ, Mosquitto.
- Topic — the “address” of a message, organized as a hierarchy. For example:
factory1/machineA/temperature. - Publish / Subscribe — a device publishes (sends) data to a topic; other devices subscribe to receive it.
Think of it this way: a temperature sensor posts to the
temperaturetopic, and the dashboard subscribes to it — every new value arrives instantly.
QoS — delivery guarantees
MQTT offers three QoS (Quality of Service) levels:
- QoS 0 — fire and forget, no guarantee. Great for high-frequency realtime display.
- QoS 1 — guaranteed at least once (may duplicate).
- QoS 2 — guaranteed exactly once. Use when every record matters.
Why is MQTT popular in IoT?
- Lightweight: tiny header, saving bandwidth and battery.
- Resilient on weak networks: supports “last will” and persistent sessions.
- Decoupled: senders and receivers don’t need to know each other, easy to scale.
MQTT at Logtek
In our demo dashboard, the browser connects to a broker over MQTT over WebSocket to illustrate a realtime data flow. Note: the real product — the Logtek Gateway G1 — collects sensor data over RS232, stores it on-site and then syncs to the server; MQTT is one of the upstream sync protocols.
Conclusion
MQTT underpins most modern IoT systems thanks to being lightweight, resilient and easy to scale. Understanding broker, topic, publish/subscribe and QoS is enough to get started. Want to see MQTT in action? Open Logtek’s demo dashboard.
Need a real-world IoT monitoring solution?
Watch the demo dashboard or contact Logtek for advice on your system.