Constrained Application Protocol
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.
What It Defines
CoAP is a lightweight RESTful protocol designed for constrained devices and IoT over UDP. Provides GET/POST/PUT/DELETE methods, confirmable/non-confirmable/acknowledgement message types, observe (server push), block-wise transfer for large payloads, and DTLS security. Designed to translate easily to/from HTTP.
Canonical (Normative)
Convenient (Practical)
Related References
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
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.
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.
NB-IoT is the cellular choice for deep coverage (underground, rural) and ultra-low-power IoT: smart meters, agricultural sensors, and asset trackers. NIDD and CoAP integration are key design decisions.