Python MQTT for IoT — ELI5

How MQTT lets your smart devices whisper messages to each other without shouting across the internet.

Imagine a bulletin board in the middle of a town square. Anyone can pin a note to the board, and anyone who is interested can walk over and read it. You do not need to know who will read your note, and readers do not need to know who wrote it. The board handles everything.

MQTT works exactly like that bulletin board, but for smart devices and computers. A temperature sensor in your garden pins a note saying “it is 22 degrees outside.” Your phone, your smart display in the kitchen, and your automated sprinkler system are all watching that section of the board. They each see the message and react in their own way.

The bulletin board has a name — it is called a broker. The broker is just a computer that receives messages and delivers them to everyone who is interested. Devices that send messages are called publishers. Devices that read messages are called subscribers. One device can be both.

The clever part is the board is organized into topics, like sections in a newspaper. Your garden sensor posts to “garden/temperature.” Your living room sensor posts to “livingroom/temperature.” Your phone subscribes only to the topics it cares about, so it is not overwhelmed by messages from every gadget in the house.

MQTT was invented for situations where devices have weak internet connections or very little power. The messages are tiny — just a few bytes — so even a sensor running on a watch battery can participate.

One thing to remember: MQTT is a bulletin board system that lets devices post and read tiny messages organized by topic, without needing to know about each other directly.

pythonmqttiotnetworking

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