Check out diabloii.net
I was having the same problem wanting to mule items. Its a small file you put in your diablo2 directory, just make sure you rename the original version to something else.
http://www.alsterlichtsatz.com/d2/d2.html
Download the d2gfx.dll from this site:
Make a new shortcut pointing to game.exe in the diablo directory. (Your normal game start shortcut points to "diabloii.exe". Do not change this, you'll need to use it as well.)
Procedure:
- backup or rename the original d2gfx.dll
- copy this special d2gfx.dll into the diablo II directory
- start up normal D2 or LOD
- host a TCP/IP game
- use "ALT-TAB" or "CTRL-ESC" or Windows Key to get out of D2 or LOD
- start up D2 or LOD with the newly created shortcut (you'll have the game running twice at the same time, off of the different short cuts. the d2gfx.dll allows this)
- join the TCP/IP game with your mule (type the displayed IP number)
- exchange items