From a first ESP32 project to a classroom lab, MQTT is the quickest way to make things talk. Start on the public shared endpoint, then move to a private broker when it gets real.
No card required
You build the project, ConnectMQ moves the data. Boards and laptops publish readings; a dashboard, a Node-RED flow or a classmate’s script subscribes — no server to set up.
lab/team-3/esp32/temperature
lab/team-3/esp32/led/setEvery step uses standard MQTT, so the same code moves from the public broker to a private one by changing the host, port and credentials.
A favourite classroom project with MQTT: an ESP32 on the lab bench at school, a Python script on a student’s laptop at home, and ConnectMQ in the middle. No firewall rules at school, no server to set up.
20:15 Student’s laptop at home
A ten-line Python script publishes a command to the team’s board.
lab/team-3/esp32/led/set → {"on":true}20:15 ESP32 on the lab bench
Subscribed to its team’s topics: it switches the LED on and publishes its state with the room temperature.
lab/team-3/esp32/state → {"led":true,"temp":24.6}20:15 Student’s script
Receives the state through ConnectMQ and prints it — the round trip takes well under a second.
20:16 The whole class
Every team has its own topics and credentials, so boards and scripts never get in each other’s way.
Start without an account: try the same script on the free public broker broker.connectmq.com:1883, then move the class to a private broker.
Machines, PLC gateways, OEE and quality data
Hubs, sensors and Home Assistant setups
Vehicle tracking, telematics and cold chain
Meters, EV chargers, solar and batteries
Smart devices you ship to your own customers
Robot fleets talking to fleet managers and AI pipelines
Power, cooling and rack environment
Streetlights, parking, air and waste sensors
Soil probes, weather stations and irrigation
Start on the public broker with no sign-up, then move the class to a private broker — the Free plan needs no card, Basic gives up to 100 connections, with TLS and its own credentials.
