I've booted up the HD version of Diablo, went into Multiplayer, and the only thing available are IPX, serial, and modem. Where is the TCP/IP option that was advertised?

I had the same question. You can do battle.NET in the classic version, not unless they have TCP/IP wrapper around IPX. I will look at it more when I get home.

Okay... that is a real bummer, honestly. Direct TCP/IP would have been ideal. Battle.net support would have been second best. Now I need to figure out how to VPN together with my friends to play together, which creates a huge technical hurdle. :(

I already owned B.net capable 640x480 Diablo 1.09. I re-bought it for the upscaling. I'll make it work. I hope the miscommunication gets resolved soon for the sake of others.

Forgive me not knowing, but:

"IPX wrapper is included that allows playing over LAN via IPX option"

Does this work over wireless?

Well so far this was a waste of $10. I'm disappointed and wish I wouldn't have bought it.

devilutionX (Diablo port on GitHub) has TCP/IP with password encryption, that might solve your problem.

Don't forget, if this sells good and blizzard goes "Oh a market on gog for old games?" then maybe they'll open up their back catalog. I dont play diablo but I'll probably buy it try and support the effort to get more blizzard games.

Yhea think i gonna get a refund too, i was so happy about this oh well

If you want proper direct TCP/IP support, replace the file named standard.snp with the same file taken from classic Starcraft. That will add TCP/IP to the multiplayer menu.

You will still need to manually enter the IP of the person hosting the game, and they will probably need to open/forward the ports used (UDP port 6112 I think? Can't remember exactly) on their router to their PC.

Just use a tunnel program like Hamachi. No port forwarding or issues or any BS. And it's free.