Proxy Server - Suggestions?

Hi guys,

I’m making a server at the moment, and I am needing to understand how the HTTP protocol works. Last time when I was learning how the Telnet protocol works I just used a proxy server to intercept all of the traffic, and the proxy server actually allowed you to view all of the data flowing through it. This allowed me to see how the protocol worked very well.

Unfortunately I have formatted my PC since, and I cannot remember the name of the proxy server application that I used - does anyone know of a proxy server that will let you look at all of the traffic that is being sent between the client and the server?

Thanks