The coap-message crate provides traits that describe readable and writable
[CoAP] messages in different levels of complexity. They are built to be used in
server and client applications as an interface between the CoAP library,
transport, and the application. Using them, the business logic of reading an
incoming request and populating the response (or vice versa in a client) can be
largely independent of the underlying CoAP library or transport.
The traits in this crate only cover the properties of CoAP at the
request/response exchange level, not of the transport specific details. In
particular, they do not expose tokens, message IDs or message types: Those are
not even present in some transports, and in general there is no need for
libraries to expose them. In the same vein, no methods are described to
allocate messages: For constrained devices, that may not even be possible, and
with CoAP libraries that support multiple configured transports, the type of
message allocated may easily depend on the intended use.
[CoAP]: http://coap.technology/