Category Archives: MQTT Protocol

MQTT is a lightweight, publish/subscribe messaging protocol designed to move small amounts of data efficiently across networks where bandwidth is scarce, latency varies, and connections are unreliable. Invented in 1999 by Andy Stanford-Clark and Arlen Nipper for connecting remote sensors over satellite links, it has since become an OASIS and ISO/IEC standard and one of the most widely used protocols in the Internet of Things.
This category is a complete technical reference for the MQTT protocol. The articles explain how MQTT actually works rather than just what it does: the decoupled publish/subscribe model and the role of the broker, the binary packet format and its 15 control packet types, topic structure and wildcards, and the three Quality of Service levels that guarantee delivery over unreliable transports. They also cover the session and reliability mechanisms (persistent sessions, retained messages, Last Will and Testament, and keep alive) and the protocol’s security layers.
A dedicated set of articles covers MQTT 5, the current version, including user properties, session and message expiry, shared subscriptions, topic aliases, the request/response pattern, flow control, and enhanced authentication.