lausvi wrote:

Has anyone managed to get Interlink server working inside DosBox, attached to a real (USB-)serial device in macOS? According to […]
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Has anyone managed to get Interlink server working inside DosBox, attached to a real (USB-)serial device in macOS? According to this blog post: https://modelrail.otenko.com/retro/dosbox-ser … -a-real-machine it should work.

I used this to attach my serial device: serial1=directserial realport:tty.usbserial

When I start intersvr, it starts Ok, but it shows no drives being shared. When I start interlnk on the other machine, a baudrate appears at the bottom of the screen, so I believe the communications are working. The client machine interlnk says it has got three drive letters mounted, but they are not readable.

Perhaps somehow interlnk can't figure out a situation where A/B drives are not there, or perhaps it can't calculate the size of drive C? (I did try setting the -freesize -argument to the mounted C-drive, but no dice).

I can't be sure, as I've never tried it, but you have to keep in mind that DOSBOX does not emulate "a hard disk" for software like this, it's closer to how the command "subst" works. If you want to make it see an actual "hard drive" you need to mount an actual hard drive image.

That link you posted actually says so.

1DOSbox happily talks to real COM Ports. We'll want DOSbox running real DOS, so follow a guide like Transmission Zero has here to install DOS to a read HDD image. Firstly, download an SVN build of DOSbox. Then download the 256mb image and get your DOS disk images here. After copying everything into the dosbox folder, grab the dosbox configuration from your user profile (you might have to boot DOSbox up once first!) and bring it over as well. I renamed the disk images to make it easier and then edited the configuration as follows:
2
3[autoexec]
4imgmount 2 "hdd-256mb.img" -size 512,63,16,520 -fs none
5boot .\D1.IMA .\D2.IMA .\D3.IMA
6
7Run DOSbox and you should be presented with the DOS installation screen. Use CTRL-F4 to rotate through disks. Finally, you should be at the DOS prompt!

I think the same. In genral, these things should work.
I've tried similar things myself in the past, but precise timing/stable emulation was important (I used fixed cycles).
https://www.youtube.com/watch?v=z9EoRA8ETUs

Another thing to keep in mind: USB-Serial adapters are what they claim to be.
They are USB to "Serial" adapters, not USB to RS-232 or USB to V.24 adapters.

While they do have a 16550 FiFO and all data lines, their levels are +5v/0v (or +3.3v/0v since more recent times).
In short they are TTL. Real old COM-Ports, by comparison, used +12v/-12v (or +15/-15v) levels.

So for maximum compatibility, mainly for DIY stuff, an external level converter is needed.
The most popular might be the MAX232 IC, but I heard some creative people even used 7805 regulators and diodes, even. 😄

Edit: I forgot to mention.. Please keep in mind that DOSBox is for games mainly, not serious applications.
Anyway, using it as a platform for other "entertainment" software (MIDI/MOD players etc) or as a tool to get an old gaming PC running should be fine, IMHO.