You can have a look at http://proxy.getwave.net/index.php?q=aHR0cDovL3hjaGF0LXdpbjMyLmJlcmxpb3MuZGUvc2V0dmFycy5odG1s, net_auth_* to know how to set proxy in xchat-gnome (those are xchat variables which are handled by xchat-gnome) -- No proxy support https://launchpad.net/bugs/31812