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 The old howto had a link pointing to outdated directplay dlls which cause problems with wine and generally don't work as expected.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.
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.