CoAP (RFC 7252)

1. Messaging model

   Confirmable, non-confirmable, acknowledgement and reset messages.

2. Request/response model

   Methods GET, POST, PUT, DELETE and response codes.

3. Message format

   Header, token, options and payload layout.

4. Reliable transmission

   Retransmission with exponential backoff.

5. Request/response semantics

   Tokens, matching and piggybacked vs separate responses.

6. CoAP URIs

   coap and coaps URIs and option definitions.

7. Proxying and caching

   Forward and reverse proxies and cache validity.

8. Securing CoAP

   DTLS-based security modes.

9. Observing resources

   Observe option for subscribing to resource state changes.

10. Block-wise transfers

    Block1 and Block2 options for large payloads.

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