Replica: A new YANG v0.90 has been released, and can be downloaded @ http://yang-online.com :

We have added the ability to now play your favorite DOS games online with YANG by creating profiles to add any of your DOS games that you would like to play online by using DOSBox.

The multiplayer types are using the “IPX Network” mode and the “Serial Null-Modem” mode.

The “Serial Null-Modem” mode is useful for games that do not have “IPX Networking” multiplayer mode, like "The Need For Speed" and the DOS version of "The Need For Speed : Special Edition" for example, so you can still play these games if it supports the "SERIAL" option.

Also games that require the use of "NETBIOS" can be played over YANG, like the "Syndicate : American Revolt" expansion and "Magic Carpet" for example, when you specify the location of your "netbios.exe" file inside the YANG setup.

If your DOS game supports in-game/lobby joining for its multiplayer mode, like "Death Rally" and "Command & Conquer" for example, this can also be enabled on your DOS game profile's settings so that players can also join your game when you are already inside the game.

Finally, YANG can also be used as a convenient way for launching single-player DOS games too.

Replica: Diablo is not a DOS game, but requires Windows, so it can't be used with DOSBox.
However Diablo has got a built-in online match-making component from Blizzard called "Battle.net".

Foxhack: ... That would be Diablo II. Diablo I didn't use Battle.net.

Protoss: I am quite sure Diablo I uses Battle.net since I played a few times via it with a Czech guy. And it was awesome.

Foxhack: Huh, well, if you say so. All I'd ever heard was that it used IPX or other forms of networking.