TinyMQTT 
Simple and lightweight (thus - tiny) MQTT server for tiny devices like ESP8266 / ESP32 running micropython. (documentation coming soon)
Features
- Fully asynchronous using uasyncio library for MicroPython.
- Tiny memory usage. So you can run it on devices like ESP8266 / ESP32 with 64K/96K of RAM onboard.
- Great unittest coverage. So you can be confident about quality :)
Requirements
- uasyncio - micropython version of async library for big brother - python3.
- uasyncio-core
- logging
More documentation and examples coming soon! :)