What is MQTT

Where it helps a business

• There are many devices on a weak link, and each must report events to the server without wasting traffic.
• The server has to receive events from devices and send them commands.

How we use it

In embedded projects MQTT links ESP32 devices with a central server: the devices publish events, and the server receives and processes them. Important logic stays on the device itself, so it keeps working if the connection drops.

Common problems

• The connection drops. A device should not depend on the server for every action; the backup channel for emergency commands is LoRa.
• An open broker. A message server without authorisation lets anyone send commands to the devices.

When you do not need it

If the "device" is a website, bot or app, MQTT is unnecessary: an ordinary API or webhooks are enough.