MQTT (Message Queue Telemetry Transport) is an ISO standard (ISO/IEC PRF 20922) publish-subscribe based “light weight” messaging protocol for use on top of the TCP/IP protocol. It is designed for connections with remote locations where a “small code footprint” is required or the network bandwidth is limited.

It’s very easy to use the MQTT protocol to exchange small messages between several EV3 devices. An explanation how to use it with python and ev3dev can be found on the website of ev3dev.org. It’s recently updated for python3.

I created a simple testapplication where one EV3-1 is controlled by the LEGO remote control for EV3. This robot sends messages about it’s movements to EV3-2. This way EV3-2 mimics the movements of EV3-1, see video below.