MQTT v5
MQTT is the dominant IoT messaging protocol. AWS IoT Core, Azure IoT Hub, Google Cloud IoT, HiveMQ, and Mosquitto all speak MQTT. Understanding QoS levels (0/1/2), retained messages, and LWT (Last Will and Testament) is essential for any IoT backend.
What It Defines
MQTT is a publish/subscribe messaging protocol optimized for low-bandwidth, high-latency, and unreliable networks. v5 adds: reason codes for all responses, user properties, shared subscriptions, topic aliases, message expiry intervals, flow control, request/response pattern, and enhanced authentication. Runs over TCP or WebSocket.
Canonical (Normative)
Convenient (Practical)
Global nonprofit consortium that develops open standards for information exchange. Publishes MQTT, AMQP, SAML, and many other widely deployed protocols. Standards go through a formal TC (Technical Committee) process.
Related Specs
CoAP is the HTTP of the IoT world — same REST semantics, fraction of the overhead. Used in NB-IoT NIDD, LwM2M device management, and any embedded system where TCP overhead is prohibitive.
LwM2M is the SNMP of IoT: the standard way to provision, monitor, and update IoT devices at scale. Used by major LPWA module vendors (Sierra Wireless, Telit, u-blox) for carrier-managed device lifecycle.