This is an example for building custom HomeKit appliances using Homebridge and ESP8266-based micro-controllers. It uses DNS-SD/Bonjour/Zeroconf for service discovery and MQTT for communication between the Homebridge plugin and the ESP8266 based micro-controller(s).

Be sure to have Docker and Docker Compose installed and running on your host, in my case a Raspberry Pi Zero W. The included docker-compose.yml defines all the required services to get started, including

• Eclipse Mosquitto, a MQTT broker.
• Avahi, a DNS-SD/Bonjour/Zeroconf service, which helps discovering the MQTT broker inside your network without fiddling with IP addresses.
• Homebridge, the actual Homebridge.

docker-compose up

mosquitto_sub -t esp8266/led/status
# => "on" or "off"

# Turn LED on
mosquitto_pub -t esp8266/led/action -m on

# Turn LED off
mosquitto_pub -t esp8266/led/action -m off

Before flashing the sketch onto your ESP8266, ensure to create a sketch/config.h based on sketch/config.example.h using your WiFi credentials. After booting and obtaining an IP, the ESP8266 searches for a MQTT broker and subscribes to it. It will blink twice once it is ready.

• https://github.com/KhaosT/HAP-NodeJS/blob/81319b35d1588453cfcb1a823805643de7df74dc/lib/gen/HomeKitTypes.js
• https://smarthome-blogger.de/tutorial/esp8266-mqtt-tutorial/