Q: is there a message library hiding in here?

[LegalizeAdulthood]

HTTP requests and responses share common structure with:

• SMTP messages
• NNTP messages

Is there a common library for all three hiding in here?

I think there are some MIME aspects to SMTP/NNTP messages that likely don't apply to HTTP, e.g. I've never heard of an HTTP request (or response) with a multipart MIME type.

[vinniefalco]

There's some stuff here that is certainly applicable to more than one RFC

https://github.com/cppalliance/http/tree/develop/include/boost/http/rfc

[LegalizeAdulthood]

Oh and I guess multipart/form-data is part of HTML...