What is MQTT? A Guide to the Smart Home Messaging Protocol
MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol designed for devices to send and receive data over the internet or a local network. It was created for situations where bandwidth is limited, devices have low processing power, or connections can be unreliable. This makes it ideal for Internet of Things (IoT) and smart home systems.
Instead of devices constantly checking for updates, MQTT works on a publish / subscribe model. This means devices send messages to a central service (called a broker), and other devices that are interested in that type of message automatically receive it.
How MQTT Works
- Broker – The central server that manages communication. Popular options include Mosquitto and HiveMQ.
- Client – Any device, sensor, or application connected to the broker.
- Topics – Messages are organised into topics, like home/livingroom/temperature.
- Publishers – Devices that send messages to a topic.
- Subscribers – Devices or apps that listen for updates on a topic.
Example: A temperature sensor publishes a reading to home/livingroom/temperature. A heating system subscribed to that topic instantly gets the update and can turn on or off.
Why Use MQTT
- Uses very little data, perfect for smart home networks, Wi-Fi or mobile networks.
- Low latency so devices respond quickly.
- Can handle unstable connections and still deliver messages.
- Works for a few devices or thousands at once.
MQTT in Smart Homes
In a smart home, MQTT can connect sensors, switches, cameras, and other devices without relying on a manufacturer’s cloud. This gives you more control, better privacy, and often faster response times.
Examples include:
- Motion sensor triggers a light.
- Smart plug reports energy usage.
- Door sensor sends alerts when opened.
Many smart home hubs like Home Assistant, OpenHAB, and NodeRED support MQTT.
How to Get Started
- Choose a broker: Install one locally (e.g. Mosquitto on a Raspberry Pi) or use a cloud service.
- Configure devices: Add your MQTT server details to your smart devices or automation platform.
- Set topics and rules: Decide what each device will publish or subscribe to.
- Test and automate: Use tools like MQTT Explorer to check messages and create automation rules.
MQTT is an advanced function that many home user will not have to worry about
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