The esp_uMQTT_broker is an MQTT broker, client, and bridge, as well as an automation controller. This video describes the ideas of the project as well as its features.
Find the code and more info on github: https://github.com/martin-ger/esp_mqtt
The pure library code for the ESP8266 Arduino environment is available here: https://github.com/martin-ger/uMQTTBr...