proxy server

hi
i am new to qt and iam familiar with c++

now my new project is learning qt by writing a proxy server:
which should be like foxyproxy in firefox : meaning : an app should connect to this proxy and this proxy should select a proxy based on requested url and connect that app through that proxy

now where should i start??
i am familiar with signal and slots and qt desighner but not with networking part of qt or c++;

if any application that is similiar to this proxy exits (with source code of course) plz tell me

thanks