A OCaml implementation of the the Constrained Application Protocol (CoAP) as defined by RFC 7252 using eio.
CoAP is a network transport protocol specialized for use with constrained nodes and constrained networks (e.g. low-power, lousy). CoAP provides a request/response interaction model similar to HTTP. However, CoAP can also be used for observing resources (see module RFC 7641) and allows bi-directional requests.
Being optimized for small and constrained devices, CoAP is designed to have small implementations. This makes it suitable for usage in embedded OCaml applications (e.g. MirageOS) and other places where code size matters.
See also the library interface.
A simple CoAP server and client is provided in the examples folder.
Start a server:
$ dune exec examples/tcp_server.exe
+New connection from: tcp:127.0.0.1:49220
+RECV: <CoAP code: 0.01
+ token: None
+ options:
+ [{number: 3;
+ value: 6c6f 6361 6c68 6f73 74};
+ {number: 11;
+ value: 6869};
+ {number: 11;
+ value: 6f63 616d 6c2d 636f 6170}]
+ payload: 4865 6c6c 6f20 436f 4150 2120 3132 3332 3133 2031 3233
+ 3132 3320 3132 3331 3233>
+Uri-Path: hi/ocaml-coap
+SEND: <CoAP code: 2.05
+ token: None
+ options: []
+ payload: 4869 2063 6f61 702d 636c 6965 6e74 21>
Use the libcoap coap-client tool (provided in the Guix development environment) to make a request:
$ coap-client -m get -e "Hello ocaml-coap!" coap+tcp://localhost:5683/hi/ocaml-coap
Hi coap-client!
Currently supports:
- TCP connection signaling messages (ping, pong, etc.)
- Block-wise transport (RFC 7959)
- Observing resources (RFC 7641)
- Resource and Service discovery (Section 7 of RFC 7252)
- TLS/dTLS
- CoAP over WebSocket
- Tests
- hyper-systems/ocaml-coap: Another work-in-progress OCaml implementation.
guix time-machine -C channels.scm --disable-authentication -- shell -Df guix.scm