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by C. Ross Jam on June 21, 2017

Saw a post on Hacker News discussing messaging. A comment mentioned Californium. Being the messaging nerd that I am, had to chase the reference. Little did I know there was a whole IETF protocol for machine to machine messaging on resource constrained devices, CoAP:

The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained networks in the Internet of Things. The protocol is designed for machine-to-machine (M2M) applications such as smart energy and building automation.

According to the IETF RFC (7252), CoAP has the following main features:

  • Web protocol fulfilling M2M requirements in constrained environments

  • UDP [RFC0768] binding with optional reliability supporting unicast and multicast requests.

  • Asynchronous message exchanges.

  • Low header overhead and parsing complexity.

  • URI and Content-type support.

  • Simple proxy and caching capabilities.

  • A stateless HTTP mapping, allowing proxies to be built providing access to CoAP resources via HTTP in a uniform way or for HTTP simple interfaces to be realized alternatively over CoAP.

  • Security binding to Datagram Transport Layer Security (DTLS) [RFC6347].

HTTPish packets over UDP with optional reliable transport.

Wonder if anybody uses CoAP in practice?

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