Mosquitto is an open source message broker that implements the MQ Telemetry Transport protocol versions 3.1 and
3.1.1. MQTT provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it
suitable for "machine to machine" messaging such as with low power sensors or mobile devices such as phones, embedded
computers or microcontrollers like the Arduino. you can see more information from this url
https://mosquitto.org/download/
v1.5.0-1#0
All
Complex license
Control