Multiplayer To get multiplayer working, you need native directplay dlls. The old howto had a link pointing to outdated directplay dlls which cause problems with wine and generally don't work as expected. However with the latest dplay from DirectX 9.0c multiplayer is (almost - see note for details) flawless.
In the wine wiki is described how to get native direct play dlls.
Personally I would recommend using winetricks directplay which installs dplay dlls and sets overwrite in winecfg, however you may choose do install manually those files in which case you need to:
Place the following dplayx.dll, dpnet.dll, dpnhpast.dll, dpwockx.dll, dplaysvr.exe in your .wine/drive_c/windows/system32
Set those files to overwrite (native, builtin) in winecfg
NOTES: The game always freezes when exiting a multiplayer game.
Sometimes when you host a TCP/IP game, no one is able to connect (any client trying receives an "IP address not found" error.) In this case just rehost and the problem will be gone.
NOTE: Heroes3HD
You can now play Heroes 3 in HD, utilizing the full size of your screen, thanks to Heroes3HD mod. It doesn't change anything gameplay wise.