letting a mirc client send like V (version) 1 Byte to a server on startup and let the server return the version number (3Bytes) isnt realy much bandwith i gues, but with millions of users it can get abit worse tough:P

ohyeah, and people could scan their data sent and check how mirc does it and then make a socketscript wich checks it like once per 30 minutes, that would make the data traffic even worse:)