Coapex

CoAP (rfc7252) stands for Constrained Application Protocol and is intended for use in embedded devices (e.g IoT stuff).

A quick (but not quite exact) comparison is "CoAP is a HTTP with binary header". CoAP supports REST as well, but it does support further things like "observation" of resources (like a Publish/Subscribe system).

Done

• Encoder: allows the user to build a CoAP binary message from a %Message struct

iex> msg = Coapex.Message.init(:request,
                       type: :con, code: :get, msg_id: 123,
                       options: [uri_host: "example.com", accept: "application/json"])
%Coapex.Message{code: :get, msg_id: 123,
 options: [uri_host: "example.com", accept: "application/json"], payload: nil,
 token: nil, type: :con, version: <<1::size(2)>>}
iex> Coapex.Encoder.encode(msg)
<<64, 1, 0, 123, 59, 101, 120, 97, 109, 112, 108, 101, 46, 99, 111, 109, 221, 1,
  3, 97, 112, 112, 108, 105, 99, 97, 116, 105, 111, 110, 47, 106, 115, 111, 110,
  255>>

• Decoder: convert a CoAP binary message into a friendly %Message struct

iex> msg = Coapex.Message.init(:request,
                       type: :con, code: :get, msg_id: 123,
                       options: [uri_host: "example.com", accept: "application/json"])
iex> bin_msg = Coapex.Encoder.encode(msg)
iex> msg = Coapex.Decoder.decode(bin_msg)
%Coapex.Message{code: :get, msg_id: 123,
 options: [uri_host: "example.com", accept: "application/json"], payload: nil,
 token: nil, type: :con, version: <<1::size(2)>>}

TODO:

• Server: understand & implement how to serve CoAP resources. Note: CoAP runs over UDP.
• Client: build a CoAP client

extra thinking

what if we turn this into a Plug-like CoAP thing?