If you like our projects, you might consider signing up to the recommended hosting service, because you’ll be supporting our work. When you sign up for Digital Ocean, you can try it for 60 days (they give you free credits to test the platform). If you don’t have a hosting account, I recommend signing up for Digital Ocean. Any hosting service that offers a Linux Ubuntu VM with full console access should work. I’ve been using it since 2015 and I personally recommend it, but you can use any other hosting service. I recommend using Digital Ocean that offers an Ubuntu server that you can manage through a command line. To run your Cloud MQTT Mosquitto Broker, you need to use a hosting service that allows you to have access to the command line and install any software that you need. You can follow this tutorial: Access Node-RED Dashboard from Anywhere using Digital Ocean Hosting Service – Digital Ocean You can also install Node-RED on the same cloud (Digital Ocean hosting account) to control and monitor your boards from anywhere in the world using your computer or your smartphone. ESP32 #1 is subscribed to that topic, so it receives board2 sensor readings.

Similarly, ESP32 #2 publishes temperature readings on the board2/temperature topic.

So, ESP32 #1 can control the ESP32 #2 outputs. The message can indicate whether ESP32 #2 should turn an output on or off.

ESP32 #1 publishes on a topic that ESP32 #2 is subscribed to ( board2/output1).Even though they are on different networks, they can communicate with each other using the Cloud MQTT broker by subscribing and publishing on the same topics.Each board is connected to a different router with access to the internet. The previous image shows two ESP32 boards on different networks.

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