Sol - An MQTT broker from scratch
rumq - MQTT ecosystem in rust.
OpenMQTTGateway - MQTT gateway for ESP8266, ESP32, Sonoff RF Bridge or Arduino with bidirectional 433mhz/315mhz/868mhz, Infrared communications, BLE, beacons detection, mi flora / mi jia compatibility, SMS & LORA.
MQTTGateway for Prometheus
Writing an aysnchronous MQTT Broker in Rust (2020)
What's Wrong with MQTT? (2018) (Lobsters)