IoT
MQTT for ESP32: How Device Messaging Fits Together
MQTT gives ESP32 projects a lightweight publish-and-subscribe messaging model that works well for telemetry and home automation.
Publish and subscribe
MQTT separates message producers from consumers through a broker. A device publishes a message to a topic, and interested clients subscribe to that topic rather than connecting every component directly to every other component.
An ESP32 might publish a sensor reading while a dashboard or automation system subscribes to it. Commands can travel through separate topics in the opposite direction.
Design topics around meaning
Use a predictable topic hierarchy and keep telemetry, state and commands conceptually distinct. Stable names make integrations easier to maintain as a project grows.
Payloads should have a defined format and units. A value without context can be ambiguous, so document whether a measurement represents percent, degrees or another quantity.
Reliability and security still matter
MQTT does not remove the need for authentication, authorization and network security. Production credentials should not be committed to source control, and command topics should be restricted to the clients that need them.
Device logic should also define behavior when the broker is unavailable. A safety-relevant local control function should not depend blindly on a successful network round trip.