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Doom2 multiplayer with 56k modem to 56k modem directly attached (is this even possible)

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First post, by mistasparkaru

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I got into real computing around 1995 when I saved up for a 486 DX33 with 4MB RAM and just about manged to play Doom2, I really wanted to play multiplayer but no-one I knew even had a PC never mind a modem. To re-live this I have bought 2 old P3 laptops and 2 external US robotics modems.

What I want to do is connect both modems together and play doom2 over the modems (I know there are easier ways but this is something I wanted to do since I started with computers nearly 30 years ago and never manged it)

I connected both modems together with a RJ11 cable and they can connect in hyperterminal and qmodem. I tied to add a 9v battery and 330 ohm resistor in parallel and it connected as normal , then in serial but this stopped the connection, so I stuck with a plain rj11 cable.

I can play doom2 multiplayer with a null serial cable but this isn't what I want to do, I want use the modems

So hers what does work
Windows 98 Hyperterminal - Hyperterminal connects
DOS or windows qmodem - qmodem connects

But all the following result in the same thing, i.e. Doom2 says connecting with the SD and RD LEDs flashing with maybe a garbled response in the modem response text in doom
Using qmodem to connect then exiting to shell and running doom2 with the already connected option
Doom2 to doom2 with the connection string AT S7=55 S0=0 V1 X0 and AT S7=55 S0=0 V1 X0 ATX0
Doom2 to doom2 with the connection string AT&F S7=55 S0=0 V1 X0 and AT&F S7=55 S0=0 V1 X0 ATX0

My modems are connected on COM1 with 0x3f8 and IRQ04 which seems to be what doom2 is looking for

I dont mind buying a phone line simulator which I have seen for about 100 GBP but I dont want to buy it, if its just my connection string thats at fault, or something else silly.

One final thing, the garbled text may be due to me trying lots of AT commands and the modem getting mixed up (which doesnt help troubleshooting)

Reply 1 of 6, by auron

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did you already read through the following links:

https://doom2.net/doom2/begmodem.html
https://www.gamers.org/dhs/helpdocs/modemstr.html
https://www.gamers.org/docs/FAQ/doomfaq/sect1.html

in particular, the last one says this:

If you STILL cannot get the modems to connect, both of you should run your favorite terminal programs, and connect with 9600, no error correction, no data compression, and NO HARDWARE FLOW CONTROL. Then just run SETUP.EXE with the "Already Connected" option in the configuration box.

Reply 2 of 6, by mistasparkaru

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Cracked it!

got it working (at 9600)

The trick was to set every setting on the modems to this
B0 E1 F1 L2 M1 Q0 V1 X0 Y0

&A1 &B0 C1 &D2 &H0 &I0 &K0
&M4 &N0 &P0 &S0 &T5 &U0 &Y1
S37=9

Then open procomm with 9600 on com1.
Then Alt+F4 in procomm to exit to dos with the line still up
Then run c:\doom2\setup.exe -com1 -9600
Then choose modem and already connected on both machines

No phone line simulator is required, just a plain RJ11 between the two modems

Reply 3 of 6, by chinny22

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Thats cool, yeh null modem makes more sense and IPX even more but this way you get sexy flashing LEDS on the modem... very important!

We have a home video where in one shot you can hear me on the phone to a mate talking comparing modem strings to get the game going as we both got modems for Christmas 😀

Reply 6 of 6, by chinny22

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I can't stop thinking about this, I'm going to have to do the same! Been looking for an excuse to use modems.

Setting up a dial up server is on my list of things to do, something like this
https://youtu.be/Bk86uqEiwpE
Annoyingly I used had free access to almost unlimited supply of the linksys VOIP phone adapters used into the video when the restaurant chain I used to work for upgraded their credit card terminals.
but it does require a fair bit of time and effort for something I'm not really going to use

But this requires no investment, time and I can get one of the kids to play with me. Also I would think this would work for any game not just Doom, Wacky Wheels for example doesn't support IPX, just modem/null modem.

Does Doom lag much? When I was doing this for real it was over rural Australian telecom network so had things like line quality , exchanges, etc slowing things down.
Now thats all bypassed I'm assuming performance is about the same as null modem?

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