From looking at your code, it appears that it is vulnerable to directory traversal attacks. If someone requests URLs like "/../../../../../../etc/passwd", you happily deliver the system's user database.

Also I'd guess that you'll get a lot of warnings if a client terminates the connection without sending a request.

However I may be wrong; I did not run your code, I only had a look at it.

I realize that you are doing this only as an exercise, but I'd strongly recommend thinking about malicious input when writing networking software.