So, my brother and I decided to buy Screamer as part of the Interplay promo. We're trying to play multiplayer, but when we select Network Mode, we can't find each other. We're on the same connection, too. Does anyone know how to get the multiplayer mode working?

Thanks for replying! IPX tunneling does have something to do with it. It turns out that there is a shortcut in the Start menu that says "Start HOST game," and another that says "Start CLIENT game." My brother and I successfully used these to play a multiplayer match.

Are your computers connected via LAN directly or by a router?
It could be possible the assigned port is blocked if it is by a router.

We're connected by a router, but the special shortcut I talked about took me to an IPX tunneling program that worked regardless.

Is it possible to play the games with more than 2 players? Are there still AI cars on the tracks?

It works in LAN, but it doesn't work on Internet. The Host can define the used port at the start, but the client cannot find the host, even the defined port is opened.

We tried it with using Tunngle, which is 100% works with other games, but not with Screamer2.

My friend and I have Screamer, and we play on the Internet fine. I just port forward UDP port 213 on my router (DOSBox's port) and give my friend my public IP address (could be found by googling "My IP Address") when he joins the game I'm hosting.

Screamer 2, I don't know as I don't have it, but if Screamer 2 uses DOSBox and has the included Multiplayer Utility (example Start > Programs > GOG.com > Screamer > Multiplayer), you can try the said port and have your friend join via your public IP address. Like I said I don't know if Screamer 2 uses DOSBox or includes the utility. If you and a friend have a bit of time, it may be worth trying.

That UDP 213 port works with any GOG DOSBox game, I also use it for Shadow Warrior Classic Complete and Duke Nukem 3D Atomic Edition. Remember, when done playing, turn the port off. Never a good idea to keep them open all the time, at least that's what I read online.