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CoAP — IoT Protocol

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CoAP: HTTP for constrained devices

CoAP (Constrained Application Protocol) is designed for microcontrollers: 8–64KB RAM, lossy wireless links (Zigbee, 6LoWPAN), battery-powered sensors. HTTP is too heavy — its text headers alone exceed some devices' RAM.

CoAP uses the same REST concepts (GET/POST/PUT/DELETE, resource URIs, response codes) but runs over UDP with a 4-byte binary header. The entire 'hello world' CoAP message fits in a single UDP datagram.

Packets in motion — click to inspect:

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