I have made the basis for a simple web server. What would i need to add to make it a proxy
That's possibly the most vague question I've seen in awhile -_-
I think a better question would be, "Why in the world did I write the webserver myself instead of using a library?"
A proxy is just a server that can forward requests to another server. So just make your server able to do that. Read up on how proxies work.
A proxy is a server that is sort of a "middle man" for requests from clients needing stuff from other servers.
My work email actually uses one of those. The email account is from our ISP, however the email itself has the company website address on it (which would be the proxy server).