MQTT won IoT messaging by keeping the broker protocol tiny and loss-tolerant

A fleet of cheap sensors and controllers sends a few bytes now and then over cellular or satellite links that drop. A heavy, chatty protocol is unusable there.

MQTT is a broker-based publish/subscribe transport: devices publish to topics, the broker routes messages to subscribers. It keeps messages small and the client tiny, and is built to connect millions of devices.

Reliability is layered in as three quality-of-service levels and persistent sessions, so a reconnect picks up where it left off. When OASIS standardized it, MQTT became a neutral option any vendor could ship.

Make the broker protocol tiny and loss-tolerant

Tiny headers and a small client footprint run on microcontrollers with minimal resources.

Publish/subscribe decouples senders from receivers, so the system scales to millions of things.

Three QoS levels let an application choose exactly-once versus cheap at-most-once.

Persistent sessions survive the flaky cellular links that IoT devices live on.

When your devices are resource-starved and your networks are lossy, win by making the protocol cheap and fault-tolerant, then let an open standards body make it neutral.

MQTT became a dominant IoT messaging standard, adopted in automotive, manufacturing, telecommunications, oil and gas and smart home, with brokers and client libraries on every major platform. Its open-standard status under OASIS made it a neutral foundation for fleets of connected devices.