This question can probably only be answered for Unix-like systems that follow the "everything is a file" idiom.
Would it be hard to create a web server that mounts local devices for handling http traffic? It would enable a program to read raw http requests from /dev/httpin (for example) and write the responses to /dev/httpout. I think this would be nice because it would allow me to create a http handler from any programming language that is capable of handling IO streams.
I don't really know where to start on this. Any suggestions on how to setup such a system?