Overview
A small IoT device network built around NodeMCU and Raspberry Pi boards, controlled from a custom Android app built in App Inventor. Every device talks to a central broker over MQTT rather than to each other directly, which is the same publish/subscribe pattern used in most real IoT deployments.
How it works
The NodeMCU and Raspberry Pi devices each connect to an MQTT broker and publish or subscribe to specific topics. The Android app, built in App Inventor, publishes commands to those topics and listens for status updates back from the devices, so a single app screen can control every device on the network without needing to know its address directly, the broker handles routing every message to whoever is subscribed.