Attached is an ebuild for xboxgw, version 1.082 xboxgw is a tunnelling application for playing Microsoft xbox system-link games over the Internet. It's currently closed- source, though the authors have expressed a desire to release source in the future. I'd suggest app-games/xboxgw for this.
Created attachment 5781 [details] xboxgw-1.082.ebuild
added to portage but with modifications http://cvs.gentoo.org/cgi-bin/viewcvs.cgi/gentoo-x86/app-games/xboxgw/xboxgw-1.082.ebuild?rev=1.1&content-type=text/vnd.viewcvs-markup