MQTT what?

Essentially the MQTT protocol is used for IoT-Devices for more in-depth info go to Wikipedia. Link

What do you need?

• an MQTT-server running
• its IP-Address

How does it work?

You publish a message to a topic on a broker identified through its IP-Address. Every device which subscribed to this topic will get the message. The structure is more like a message board.

Example Tutorials

MQTT Communication between multiple ESP´s with Raspberry Pi as broker