detect network activity and hibernate if none

I am building a file and printer server at home and would like to be able to suspend ou preferably hibernate it when it's not being used. However, since it's a server, no one will ever move the mouse or press any key. Is there a way to timeout after 'x' minutes of no traffic and run a command to hibernate?

Also, as a separate question, to turn the server on I know I can send a WOL packet, is there a way to do this automatically as soon as the server is accessed?

Last but not least, I wanted to make a windows server, but I wouldn't mind much building a linux server if I can do the things above.