/ˌɛm.kjuːˌtiːˈtiː/
noun — "lightweight messaging protocol for IoT devices."
MQTT , short for Message Queuing Telemetry Transport, is a lightweight, publish-subscribe messaging protocol optimized for constrained devices and low-bandwidth, high-latency, or unreliable networks. It enables efficient, asynchronous communication between clients and brokers, making it widely used in Internet of Things (IoT) applications.
Technically, MQTT operates over TCP/IP and defines three types of Quality of Service (QoS) levels: at-most-once, at-least-once, and exactly-once. Messages are published to topics, and subscribers receive messages from topics they are interested in. The protocol uses a small header (just 2 bytes for most messages), minimizing overhead and allowing reliable messaging even on limited hardware.
An MQTT system consists of clients (publishers and subscribers) and a broker. Publishers send messages to topics on the broker, which manages delivery to subscribers. The broker can retain messages for new subscribers, support persistent sessions, and handle thousands of concurrent connections efficiently.
In workflow terms, a temperature sensor in a smart home might publish readings to a topic named home/temperature. Multiple subscribers, such as a monitoring dashboard, an alerting system, or a logging service, receive the readings independently and in near real-time. Publishers and subscribers are decoupled, allowing each component to scale or fail without impacting the others.
Conceptually, MQTT is a minimalist switchboard for device-to-device messaging, designed to keep communication reliable, low-overhead, and asynchronous across large networks of sensors and actuators.