I'm learning about network programming. Specifically proxy servers. I've created a very rudimentary proxy server on my mobile phone. However I think there's some proxy server basics that I don't know that will help me create a more robust proxy server.
What I've done so far: server on my mobile device listens for requests from laptop. When server receives a request like www.google.com the web page contents are fetched and returned to the client on the laptop. The client then opens the page contents in a desktop browser.
I think the sending/receiving of requests can happen on a lower OSI model layer (perhaps transport). How can I create a more robust proxy server? (one that just sends and receives bytes and doesn't care/know about HTTP)
A proxy server runs at the same layer as the protocol being proxied. It seems you are talking about an HTTP proxy. HTTP runs over TCP, and so does an HTTP proxy.
Define 'more robust'. What have you done so far?
An HTTP proxy server is a pretty simple thing, unless it has elaborate logging, caching, etc. The basis of it is (1) something to recognize and action the GET/POST/PUT/CONNECT etc. commands and (2) thereafter just copying bytes in both directions simultaneously.