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File transfers via the parallel port on DOS using LapLink

by fcambus on 4/13/22, 12:12 PM with 119 comments

  • by wmitty on 4/13/22, 3:25 PM

    Laplink had a really neat feature for when you didn't have your laplink install disk with you (or had the wrong size laplink install disk).

    You could connect the two computers with a RS232 null modem cable, then type something like the following on the target computer:

    mode COM1:2400,n,8,1,p

    ctty COM1

    This redirected the input/output for the terminal to the serial port.

    Laplink on the source computer would then 'type' a series of console commands to create a simple transfer program on the target computer. It would use this simple transfer program to transfer the full laplink.

    IIRC it used the msdos DEBUG.COM to build the transfer program on the target computer (but this is an old memory, so could easily be a reconstruction).

    Composing this message is bringing back lots of weird memories about how we used to compute before the internet.

  • by wdrw on 4/13/22, 1:18 PM

    The parallel port was wonderfully hackable. Having your PC control an LED light, or even a motor (with some effort), didn't take a whole lot of electronics knowledge. Or 8 LEDs, one per pin. And controlling it was as easy as sending text to a printer. We lost this in the age of USB...

    When I was a kid my dad helped me hook up a pin to a motor. And not just any motor, but one inside a cassette tape player. I could then make little games in BASIC that had real voice! Of course it had to be linear, it basically played chunks of voice recording and stopped at the right times.

  • by FullyFunctional on 4/13/22, 2:35 PM

    Linux support IP over the same cable, it's known as PLIP, parallel-port Internet. It was the only way to access the outside world on my Toshiba T1800 laptop. However it wasn't fast (23 kB/s IIRC) and it completely bogged down the host (no hardware acceleration there).

    There were experimental work on "8-bit PLIP", but the hardware wasn't very standard and in my testing it wasn't actually faster in practice. There was also some kind of DMA standard for the parallel port, but I don't think anyone succeeded in exploiting it for PLIP.

    The who PLIP experience gave me a new appreciation for IBM's hardware accelerated "channels" concept - something we never got with x86 given its origin.

  • by bcrl on 4/13/22, 1:02 PM

    The first x86 system I had was a hand me down 286. The parallel port on the motherboard was only unidirectional, so I modified it to be bidirectional by soldering a bodge wire between the output enable signal on one of the 74LS374 (I think) and the other control register. Ah, old systems were so hackable in the 1980s prior to the mass migration to large scale SoCs.

  • by sponaugle on 4/13/22, 2:58 PM

    There was a lot you could do with the parallel port. I was a coauthor on a paper about using parallel ports to interconnect computers to provide barrier synchronization for large parallel computing projects. It was a surprisingly fast way of getting a bunch of single bit synchronizations across a bunch of machines. This was back in the early 90s.

    link - https://ieeexplore.ieee.org/document/4115699

  • by phendrenad2 on 4/13/22, 4:42 PM

    Parallel port was great. It's super annoying that USB-to-Parallel adapters cut corners and only transmit the bare minimum signals to print to an inkjet printer. There was a rich ecosystem of parallel port devices out there, including MIDI and SCSI adapters, even ethernet ports. But none of them work through USB adapters.

  • by dmeybohm on 4/13/22, 2:34 PM

    I wrote a utility to copy small files from Linux -> DOS over a LapLink cable.

    https://github.com/dmeybohm/ppcopy

    I used it to fix a Windows 98 laptop that wasn't booting all the way to Windows. The would boot to a DOS prompt only, there was no CD-ROM driver, and I only had a Windows 98 install CD. So, there was no to re-install Windows to fix it.

    So I wrote the assembly copier for the parallel port. I think it was about 200-500 bytes. Then I used dos DEBUG.EXE to write the hexadecimal code for the program into memory and then write the .COM program to disk. Surprisingly, I didn't make any mistakes (or any that mattered...) and it worked the first time. I had also done a checksum in the copy program in case I screwed it up. But it took about an hour to write the program into DOS debug.exe.

  • by mwexler on 4/13/22, 1:02 PM

    I loved the kit: easy to use software with a hydra cable that linked to everything available at the time (which was basically serial and parallel printer ports). Did many migrations with this thing. I remember one friend asked me to bring over "your computer jumper cables" to help migrate.

  • by ThinkingGuy on 4/13/22, 2:31 PM

    At my first desktop support job, we used to back up users' laptops over the parallel port to a blank drive on another computer.

    One time, I got the command line parameters wrong, and accidentally ran the copy in the opposite direction, overwriting a senior manager's disk drive with a blank disk image. It was the first "big mistake" of my IT career.

  • by unixhero on 4/13/22, 12:57 PM

    Laplink was so great and always worked. The only thing was the lack of possibility to play games over parralell link, only serial was possible. That is not laplinks' fault but rather the technology. Naturally parallell 25 pin cables had a much higher throughoutput rate than serial 9pin links had.

  • by jgrahamc on 4/13/22, 12:56 PM

    We've got so used to WiFi, GSM and Bluetooth that people forget how robust wired connections are.

  • by Starwatcher2001 on 4/13/22, 2:19 PM

    Good old laplink. I've still got a "hydra" cable in my desk drawer.

    Back in the 90s I used the parallel port to interface a PC to a TRS-80 to allow me to store games on the PC. As another commenter has mentioned, the parallel cable isn't fully bidirectional so I used the printer ready, paper out and other signals as imput lines and wrote a nybble (half a byte) based protocol between the two. Fun times.

  • by api on 4/13/22, 3:39 PM

    I migrated data off a dying PC once onto a new one in a pinch by using two paperclips to cross the TX/RX pins of both computers' serial ports while they were back to back. Then I used PC Anywhere (another fine bit of software) to do the file transfer. Took about 24 hours but moved everything fine.

    Year was 1997 I think.

  • by hed on 4/13/22, 2:24 PM

    My best use of LapLink was as a teen helping migrate a library off an old system. I think it was using NetWare 2.x with some DOS emulation for a library card catalog. Couldn't get it to talk IPX to the existing NetWare stuff (5.x) we were migrating to. But the DOS emulation was complete enough for us to install LapLink and bring over the files for the program!

    I still have the yellow parallel cable and blue serial cables at my parents' house.

    Also pretty sure I used the blue cable to do Command & Conquer over null modem to the next room at home before I figured out how to install IPX/SPX and get the machines to talk over the 10Base2 that was between them.

  • by fortran77 on 4/13/22, 1:39 PM

    LaPlink (as we called it) was such a useful utility back before wireless and even before ethernet.

    And they're still in business: https://web.laplink.com/

  • by andix on 4/13/22, 2:02 PM

    I always used INTERLNK, which was included with MS-DOS 6.22. I think you could even just copy the exe to older DOS versions and it would just work.

  • by scurraorbis on 4/14/22, 8:09 AM

    I really like the UX/UI of the transfer tool. The dialog meant for literate people that explains in clear terms what the problem is and what can be done about it is a breath of fresh air coming from our world where "the user is stupid" toy-like UIs dominate.

  • by awiesenhofer on 4/13/22, 2:41 PM

    Oh what a blast from the past - copying files with blazingly fast 1MB/s!

    If you prefer a Windows GUI to this, Total Commander has full support for Laplink (still) built in:

    https://www.ghisler.com/efaqport.htm

  • by jacquesm on 4/13/22, 1:12 PM

  • by tristor on 4/13/22, 4:57 PM

    Oh wow, this brought back memories. I remember using LapLink to transfer files from our family desktop to a used Toshiba 286 laptop that my parents found for me over a parallel cable so I could mirror the setup.

    I ended up using this tool multiple times over the years, and even well into the Win2k / Win98 days, it was still a more reliable method for transferring files between computers on WinTel systems vs other methods. Sometime in the Win2k days I transitioned to using a crossover Ethernet cable and setting up an FTP server on the origin system.

  • by danrl on 4/13/22, 1:20 PM

    Nostalgic! I used LapLink a lot back in the days. When Ethernet became affordable I was baffled by the speed of data transfer. Lightning fast!

    Written from a mobile phone with 5G. Tell me about exponential growth.

  • by JoeAltmaier on 4/13/22, 3:25 PM

    I tried to make a high-speed bus between a pair of computers using the parallel port once. But I couldn't get any appreciable bandwidth out of it. Turns out the hardware I was using (CTOS/BTOS workstation) had a capacitor on a critical line. To reduce noise the hardware guy said. But it severely limited the maximum transfer rate. On the widest connector available at the time! Printers don't need to go that fast, he said.

    Anyway it still seems like a lost opportunity, years later.

  • by bane on 4/13/22, 10:04 PM

    oh man, this brings back some memories. In the early-mid 90s I worked at a mom-n-pop computer repair store and LapLink at some point became sort of a standard tool for all sorts of system setup and configuration stuff.

    Keep in mind that other data transfer options were generally disks of some sort that held less than 1.5MB of data and were very slow to write/read. It wasn't too important at the beginning as most systems with hard drives were generally only a few MB anyways.

    But storage moves fast and software bloats quick and it wasn't too long before we were shuffling a couple dozen disks worth of stuff onto new system builds or worse, between systems as people migrated. Optical wasn't really an option for lots of reasons, most notably very expensive and at the time generally SCSI and tended to be exotic WORM drives. Almost nobody in the consume market had SCSI in the IBM-PC compatibles, and the disks were $30-40 each if you managed to write one successfully.

    LapLink filled the gap for a couple of years instead. Connect the cable, boot to a couple of prepared floppies and start transferring. Really quite reliable even if it was slow.

    Eventually it became so slow, and we realized "hey we work in a shop where we can take the hardware apart anyways" and just started mounting the harddrives with the data to transfer from into the system with the new volume and using xcopy or eventually a clone tool.

    I think even that finally fell out of favor once rewritable IDE CDs became common, plus zip/jazz etc. drives, and eventually windows started shipping with a network stack, but I was long out of that business by then.

  • by bluedino on 4/13/22, 1:59 PM

    Had some fun one time making a boot floppy to install Linux from a parallel port CD-ROM or Zip drive

    https://tldp.org/LDP/Mobile-Guide/html/mobile-guide-p1c3s4-i...

    Worked great in the days when networking equipment was still expensive

  • by fatnoah on 4/13/22, 1:40 PM

    Wow, this takes me back to my freshman year of college in 1993 and trying to connect computers in different dorm rooms with lengthy serial cables. We eventually got it to work, but I remember it took a couple days of tinkering.

    In the summer after that year, the school networked all of the on campus housing via ethernet, so connecting things the following year was much easier.

  • by raffraffraff on 4/13/22, 2:20 PM

    Jesus, HN has been a nostalgia machine recently. That's another thing I didn't realise I had forgotten.

  • by anotherevan on 4/14/22, 2:30 AM

    I have vague memories of doing this.

    For my final year project in university I made a signal generator that was controlled via the parallel port. Would create the desired waveform in a GUI DOS program, then download via the parallel port. Would also start/stop the signal generator via computer.

  • by deelowe on 4/13/22, 3:00 PM

    Early in my career, I spent an extraordinary amount of time as a co-op in a factory running around backing up logs and various other items using LapLink. If we ignore the manual labor part of it, it was a fairly decent system for weekly cold backups (our warm back-up solution was network based).

  • by pjmlp on 4/13/22, 2:06 PM

    Now that is a travel to my teenage years

  • by malkia on 4/13/22, 5:17 PM

    I used this few times, when I was a kid in one of our local PC computer clubs. It was magic to me. There were some alternatives, and friend of mine was using something "kermit"-based (protocol?). That was years before internet really came to my city for real.

  • by 1970-01-01 on 4/13/22, 3:01 PM

    LapLink was a great idea and solved a very real problem: You could not copy large files (anything larger than 1.44MB) around without this, tape, or modem (and when it worked you felt it was finally time to build that Ethernet network).

  • by systems_glitch on 4/13/22, 5:02 PM

    This works with Microsoft's INTERLNK/INTERSVR as well. As others have mentioned, this was our first form of networking at home! Even had a special DB25 punchout wall plate to make the non-basement end more presentable.

  • by akudlacek on 4/13/22, 9:22 PM

    Not as convenient for transfering from a modern Windows 10 to MS-DOS. I ran into this problem and used Kermit and teraterm. Teraterm has ability to transfer over a couple different protocols.

  • by chrisstanchak on 4/13/22, 11:07 PM

    Ah, the days of hauling my massive tower over to friend's houses and sharing programs we downloaded on BBSs via Laplink. Good times.

  • by raintrees on 4/13/22, 2:59 PM

    I still have my custom-made 20' cable for laplink over parallel ports...

    Those were the days.

  • by outside1234 on 4/14/22, 12:09 AM

    Holy cow - totally forgot about this. Thanks for the memory lane.

  • by hestefisk on 4/14/22, 12:19 AM

    Oh man the nostalgia. Took me right back to my childhood.

  • by jaimex2 on 4/13/22, 10:05 PM

    Remote install on Laplink was the bomb.