Basicly, TetriNET is a Multiplayer version of Tetris, and its LAN use-able.
So im gonna give the public the links:
-To download Hamachi (optional, for LAN thru net) :
http://hamachi.en.softonic.com
-To download a TetriNET client (Go with the TetriNET 1.13, thats what im using) :
http://en.tetrinet.no/tetrinet-1-13-page-14.php
And now, for the connection guide.
1.Open up TetriNET and chose "Client options".
2.Type in where it asks you for a Server IP "tetrinet.us" and then your i-doser forum name.
3.Connect, and join/create the "idoser" channel by typing in "/join #idoser" in the Partyline.
4.Find a name you recognize, and challenge them!
5.Enjoy!
Steinar.hrafn at gmail dot com if you got questions!
-Steinz