Well I did it once but that was years ago, not sure if this is ok for connecting newer computers:-
I have a modem that connects to one computer on a USB port, and from the modem a cable Rj-45 plug goes to a 3 coms PCI card in the 2nd computer.
Now I have an ethernet cable with Rj-45 plugs, can I just connect to the lan ports on each computer if one computer is gigabyte ethernet and the other is 3 coms?