MQTT vs HTTP vs CoAP: choosing an IoT protocol

MQTT

A lightweight publish/subscribe protocol that runs over TCP and routes messages through a broker. It offers three delivery levels (at most once, at least once, exactly once) and suits many devices sending small messages on unreliable links.

HTTP

The web’s request/response protocol. Universally supported and easy to debug, but heavier for tiny devices and not designed for pushing messages to them.

CoAP

A protocol modelled on HTTP but built for constrained devices and networks, running over UDP. It keeps the familiar request/response style with a much smaller footprint.

Choosing

1. Many devices, small frequent messages, need to push to devices: MQTT.
2. Existing web infrastructure and larger, less frequent exchanges: HTTP.
3. Very constrained devices and lossy networks: CoAP.
4. Whichever you choose, secure it with TLS or DTLS and authenticate devices.

IICTP is a new independent credential and is not ISO/IEC 17024 accredited.