control process network I/O

[-[Myth]-]

I have a closed source server program (win32, console) that i would like to
add some additional features to. I already have code to redirect stdin,out
etc so i can control it in that way, but i would also like to have it set
up so that all incoming connections are accepted by my parent process,
which then checks that they are not from banned IPs etc and then just lets
them pass through to the server. I would then be able to implement new
features by catching all incoming messages starting with a certain code and
doing whatever must be done...

I hope you can under stand all that

I'm thinking that this must be possible because software firewalls (eg
ZoneAlarm) do roughly the same thing.

Thanks in advance.