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Mosquitto (MQTT broker)

Lightweight message bus for IoT — Shelly, Tasmota, ESPHome, Victron, and most "smart" devices speak MQTT.

What it does

MQTT is a lightweight message bus that IoT devices use to publish their state and subscribe to commands. Most DIY van sensors (Shelly relays, Tasmota-flashed devices, ESPHome boards, Victron kits) talk MQTT. A broker (typically Mosquitto) runs on your network and relays messages between them. Home Assistant also speaks MQTT and can mirror every device into a clean entity.

How to install

  1. The official Mosquitto add-on installs in one click from the Home Assistant Add-on Store.
  2. Default port is 1883. Devices on the same network can publish without extra config.
  3. Set a username and password — MQTT has no security otherwise.

How it works

Devices connect to the broker and either publish state (e.g. shellies/living-room/light/state → ON) or subscribe to commands (e.g. shellies/living-room/light/command ← OFF). Home Assistant subscribes to everything and shows each topic as an entity.