Multiplayer with DOSBox

[rnlf]

#8715

Just a quick guide on how to get multiplayer working in DOSBox!

Disclaimer, I’ve only tested it on a single PC, I cannot yet say how well it behaves with internet latencies, especially if the two players are far apart on the globe. It should definitely work, but if it’s playable, we’ll see 😉

The idea is that one DOSBox opens a TCP server for the other to connect to. That means, we need to reserve a port for it and make sure the port is open on the router and forwarded to the PC that is hosting the server. This is router specific, so I can’t really help with it, but you probably know how it works for your router 😉

Anyway, once we picked a port and opened it on the router, here is how to connect DOSBox and subsequently Wacky Wheels to the other computer:

1. Start the DOSBox serial server on one machine. Boot up DOSBox as usual, then enter the following command:

serial 1 nullmodem port:1234

The port number must be the same that has been opened up on the router.

2. Connect the DOSBox virtual nullmodem from the other machine. Boot up DOSBox as usual, then enter the following command:

serial 1 nullmodem server:123.123.123.13 port:1234

The IP address must be the public IP of the host (find out by asking your router or use a service like What’s my IP

The port must be the one that has been configured on the host’s router to forward to DOSBox. If you set it to forward port 1234 to 1234, then use 1234, if you set it to forward 4321 to 1234, use 4321.

3. Configure both WW games. Start SETUP.EXE and select “Modem/Serial setup”, then “Serial link setup”, finally pick “Com1”. None of the other options need to be touched.

4. Start both WW games. Start WW.EXE, skip all the intros and go to “COMM-BAT™ PLAY”. Pick “SERIAL CABLE” on both machines.

5. On one of the machines, pick “WAIT FOR CONNECTION”, then select “57600 BAUD”.

6. When it shows “SYNC IN PROGRESS” on the host, pick “MAKE CONNECTION” on the other machine and also select “57600 BAUD”.

7. If everything goes well, you should see “REMOTE IS CONTROLLING THE MENU” on the host and be able to control the game from the other machine.

8. PROFIT

[jadi]

#8717

Thanks. Reading this was joyful. I did not know how the serial thing works. Very cool and thanks for taking time and writing all the details.

[TigerQuoll]

#8725

I tried a game between two physical machines using a null-model cable the other day. I was surprised by how technical it was. It CAN be done much easier – other programs of the era could communicate via serial and were almost entirely self-configuring. Basically PnP.

I had to set the speed in Wacky Wheels down to a ludicrous 9600 baud. Higher than that and the droupouts were unacceptable, causing the games to quickly become desynced, or they just wouldn’t connect at all.

The two computers, I might add, were right next to each other and the cable is I think about 1 metre long. (Maybe my cable just needs a ferrite bead?)

This might also explain why the physics are so granular – too many floating point coordinates would probably just make multiplayer completely unplayable due to sync issues.

[rnlf]

#8727

We played a little test session with DOSBox over the internet yesterday and it worked flawlessly! At least between Tijn and me and we’re only a couple 100km apart.

Real hardware can be a pain 😉

[rnlf]

#8735

So, sadly it seems to be very ping sensitive. Tijn and I tried it through a proxy in a third city and the added latency made it unplayable. It seems we have just been at the edge of what’s possible to play on the internet 🙁

That’s very sad, because it means we can’t really have our tournament.

[TigerQuoll]

#8739

There’s the “play via modem” option as well. Is there some way to rig a fake modem connection over DOSBox? And is that likely to work any better?

[rnlf]

#8740

Yeah, good question. Need to research modem connections in DOSBox, but my assumption is that it would be subject to the same latency requirements – and a “real” direct modem connection between two players would have had pretty low latency compared to an internet connection.

But I’ll take a look at it!

[firefyte]

#8741

Has someone tried split screen via proton/steam?