EMQ (Erlang MQTT Broker) is a distributed, massively scalable, highly extensible MQTT message broker written in Erlang/OTP.
EMQ is fully open source and licensed under Apache Version 2.0. EMQ implements both MQTT V3.1 and V3.1.1 protocol specifications and supports MQTT-SN, CoAP, WebSocket, STOMP, and SockJS at the same time.