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Old 25 May 2019, 10:57   #1
theq
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Null modem over WiFi/Internet

With games like Lotus and Skidmarks being multiplayer games with a null modem cable, are there any of the "serial to wifi"-devices out there such as WiModem232 that work with these games over WiFi/Internet?
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Old 25 May 2019, 12:45   #2
lesta_smsc
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I believe myself and others have asked this question before. Latency is the issue.
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Old 26 May 2019, 03:35   #3
bbond007
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Quote:
Originally Posted by theq View Post
With games like Lotus and Skidmarks being multiplayer games with a null modem cable, are there any of the "serial to wifi"-devices out there such as WiModem232 that work with these games over WiFi/Internet?
I believe you would able to do this if you connected your Amiga to a Raspberry Pi using a USB serial adapter and null modem adapter.

Using the UDP protocol offers the lowest level of latency. Ethernet offers less latency than WiFi...

I have written a program called 'MidiLink' which is really designed for the MiSTer FPGA platform, but could also easily run on a Raspberry Pi.

You could probably even just use 'socat' which is included in most distros.

https://github.com/bbond007/MiSTer_MidiLink

I have gotten the following games working (on the MiSter Minimig core) and probably a few I cant remember ATM:

Knight of the Sky
Fire Power
Skidmarks AGA
Battle Chess 1
Battle Chess 2
Populous

I have even played the Amiga version of Populous against the DOS PC version - Obviously I made the PC evil.

Lotus Turbo Challenge probably won't work. I'm not sure if it uses any standard serial protocol. So far I have not figured it out

If you have been following the WiModem232 thread it seems like the device may have too much latency for some games such as Knights of the Sky...

Last edited by bbond007; 26 May 2019 at 03:58.
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Old 26 May 2019, 08:43   #4
theq
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Latency is the issue.
Wasn't really planing a internet service but for the fun of it.
However, my initial idea was to be able to play between rooms at home without having to lay out extra cabling. And since everything is on IP these days...

Quote:
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I believe you would able to do this if you connected your Amiga to a Raspberry Pi using a USB serial adapter and null modem adapter.
I have read about this solution but couldn't see this as feasible for Amiga games over IP. I will have this a go now, though. Got some Raspberry Pi's laying about.

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I have even played the Amiga version of Populous against the DOS PC version - Obviously I made the PC evil.
Wouldn't have done it any other way myself.

Thanks for the response and I will eventually report back my findings. Need to land some of my other projects first.
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Old 26 May 2019, 09:05   #5
Toni Wilen
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Serial link games that are designed to work with modem connection probably work fine but games like Lotus II require very small latency (in range of about few milliseconds max)
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Old 26 May 2019, 09:32   #6
theq
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Serial link games that are designed to work with modem connection probably work fine but games like Lotus II require very small latency (in range of about few milliseconds max)
Might be a high baud rate requirement. Probably 115200 or something higher than "common of the time" rates for modems (i.e. 33600).

No clue how those games were programmed, but my guess is that "2 player"-positioning isn't stored in a FIFO-buffer with time stamps etc (as if I know any programming).
Wouldn't this be evident if there was a frame rate drop with variable latency? Or if properly programmed it just disregards "2 player" all together. Will experiment when the day comes.
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Old 26 May 2019, 09:45   #7
Toni Wilen
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Lotus II becomes totally unplayable if latency is too high and sooner or later if will stop working.

I don't remember Lotus II using fast baud rates and I haven't examined how it works but I'd assume it sends and receives at the same time, one packet per frame and expects both sending and receiving have almost identical timing.

Note that Stunt car racer uses 9-bit mode (start bit, 9 data bits, 1 stop bit) which is incompatible with normal PC serial ports.
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Old 26 May 2019, 10:59   #8
theq
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Quote:
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Lotus II becomes totally unplayable if latency is too high and sooner or later if will stop working.

I don't remember Lotus II using fast baud rates and I haven't examined how it works but I'd assume it sends and receives at the same time, one packet per frame and expects both sending and receiving have almost identical timing.
That would make sense knowing the limitations and expectations of that ear.

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Originally Posted by Toni Wilen View Post
Note that Stunt car racer uses 9-bit mode (start bit, 9 data bits, 1 stop bit) which is incompatible with normal PC serial ports.
Good to know, thanks!
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Old 26 May 2019, 17:31   #9
sean_sk
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Lotus 2 serial link uses 9600 baud but, as Toni mentioned, requires very tiny latency.
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Old 02 June 2019, 13:14   #10
lesta_smsc
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Lotus 2 works using 2 instances of WINUAE on the same PC. I'd imagine via Ethernet it might be possible over IP. Not tried... but others have managed to connect WinUAE to real Amiga to play Lotus 2 and it works.
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Old 03 June 2019, 13:34   #11
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Lotus 2 works using 2 instances of WINUAE on the same PC. I'd imagine via Ethernet it might be possible over IP. Not tried... but others have managed to connect WinUAE to real Amiga to play Lotus 2 and it works.
I tried 9600 baud on my two MiSTer running Minimig core with my MidiLink program using UDP protocol over ethernet - plugged into the same HUB.

Still did not work. It did not even start. I suppose could still be latency as Toni said...

I also remember (back in the day) that I had to use a different null serial cable than I normally used. I was connecting an A500 to an A1000

I borrowed a cable from work that came packaged with a product we used called "LapLink" for transferring files between DOS computers. If its expecting to sync using RTS/CTS, DTR//DSR or DCD/DTE than its just not going to work with any type of modem connection - which transfer data but not the status of those control lines.

Last edited by bbond007; 03 June 2019 at 13:59.
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