Now you know how clients and servers work in some detail. There is a great deal more to learn, but that is mainly in local system specific details. The basics are all here.
There are new releases of servers regularly, and new tools become available all the time. If you have a problem, or need a new tool, the chances are someone else had the same need, and if you're lucky, someone has already solved it. Check the online documentation about the server you're using, and don't forget that CGI programs from one server should work on another.