Is it possible to connect an old 386 machine to network (ethernet)? It has only parallel and serial ports. I'm not expecting much, just planning to use it as a remote terminal. The machine in question is a Commodore C386SX-LT
One option is to use a modern Linux board to act as a fake modem connected to serial port. Then you can use any old software that would connect to internet by a modem connection, without actually having to pay the massive phone bills of the 1990s.
The software setup is not very complex, mainly requiring installing
ppp server on Linux. There is also a tutorial for building a PiModem out of Raspberry Pi.
Hardware-wise, you need to get the correct signals connected, match the voltage levels and ensure that handshaking works. Handshaking is especially important as a 386 might not be up to continuously handling the full 115kbps of data, considering fastest modems were only half that speed. Depending on the UART used on the 386, you might even be able to get 230 kbps or higher baudrates working.
Since it's a pretty early laptop without a PCMCIA port, there won't be a way to add an Ethernet port. Your best approach is to use the serial port to connect via null-modem cable to a modern machine that either has an RS-232 serial port, or has hardware and drivers for bridging its USB port to RS-232 serial. Once the two are connected, use of the laptop as a terminal should be a trivial matter of running a terminal server on the modern machine and a terminal emulator, probably under MS-DOS, on the laptop (i.e. ProComm).
If you want to transfer files, there are Z-modem implementations on modern Linux machines, and probably for Windows too. So you can use a Z-modem capable DOS terminal emulator to easily transfer files at perhaps blazing speeds of 115 kbps.
Going beyond simple file transfer, FreeDOS could be installed on the laptop along with TCP/IP, PPP, and applications like
wget if you wanted to connect the laptop to the Internet. Again, a Linux peer can be the bridge for this, effectively simulating an old "dial-up" type of Internet connection for the laptop. Setup is much more complicated than just using the terminal emulator approach.
If you really want to use the Parallel port, you could try to get LapLink going. This would be the period-correct way of connecting a laptop to a desktop. But your desktop will need to be able to run either very old LapLink software, or a modern work-alike (I know of none). Alternatively, MS-DOS 6.22 has INTERLNK.EXE, if you can run its server using MS-DOS emulation on your desktop. This was Microsoft's answer to LapLink back in the day...
Things get more interesting if the laptop has a PCMCIA port or built-in Ethernet. Obviously such machines are still pretty compatible with modern networking, especially if you can run TCP/IP. You could even just install Linux on such a laptop, and then it would be "plug-and-play" with modern computers, sort of... such setups require patience to get going and fail on first contact with modern SSL implementations.
Assuming you're looking to put your laptop on the internet as opposed to just do file transfers or some such, there are a couple of DOS TCP/IP stacks. If you're lucky, you can find one of the Xircom PIO ethernet controllers. More likely, you'll do it over the serial port.
- You're looking for an IP stack that supports SLIP or PPP, which are IP-over-serial standards. Once such open source package is mTCP which also includes a selection of client programs (e.g. FTP).
- You'll need a router of some sort between serial and ethernet. Linux can do this just fine, and probably the easiest and best documented way to do this.
- You'll need a serial "null modem cable" to attach the laptop to the router.
Depending on what DOS stack you end up, you'll then do something like the following on the router to bring the link up:
pppd -detach crtscts lock proxyarp local IP:remote IP /dev/ttyS3 38400 &
Fortunately, there's a lot of documentation once you're on track.