MQTT
Problem
A tiny battery-powered sensor sends temperature readings over an unreliable network.
A heavyweight application protocol would waste bandwidth and energy.
Solution — MQTT
MQTT historically stands for Message Queuing Telemetry Transport; today, the standard uses simply MQTT as its name.
MQTT provides lightweight publish/subscribe messaging through a broker.
For example, home sensors publish temperature readings, while smart lights receive on/off commands.
Sensor → topic → Broker → Consumers
Core idea: MQTT provides lightweight messaging particularly suited to constrained devices and unreliable links.