This post will tell you everything you need to know about MQTT communication which will enable you to use it communicate between devices.

Make an EC/pH/ORP/temperature sensor device to monitor water. Interact with it through a website using Bluetooth Low Energy.

Learn how to use Arduino IoT Cloud and Amazon Alexa to switch the channel, adjust the volume and turn on or off any TV.

As a follow up to the room thermometer project, we write a sketch that communicates with an online weather service and displays the weather.