That’s what laplink was created for - I still have a pair of laplink cables, one for Serial to Serial, one for Parallel to Parallel (the latter was an order of magnitute faster than serial)…
I still use that laplink serial cable - as a console cable to either of my Sun Sparc machines when I power them up… i.e. a “null modem” cable…
I once saw an acoustic coupler modem at a “trash and treasure” market in a carpark - kinda wish I’d got it just for the retro vibes… I never used one…
I did use dial up to a 300 baud modem pool at my university - but my modem was 14400 baud (it was an 8 bit ISA modem card). It was painfully slow… If I actually need to get a file from my $HOME on campus - I used sneakernet instead - i.e. I drove or rode (motorcycle) and copied it to floppies - that was WAY faster than 300 baud! I think the UNIX download program we used was “zmodem” - the main app I used has both DOS and Windows versions - can’t remember the name - all I know is that it was written and compiled in Pascal (it might have been “Telix” I think - I used it to dial up BBS). I can’t remember what UNIX it was we dialled into - might have been AIX or SunOS…
If I remember correctly they were yellow and blue depending on the connection used. Gosh not thought about laplink for years, they used to be in my good to go kit, no idea where they are now suspect the bin during a house move.
the blue serial cable (null modem) had both nine pin, and 15 pin connectors on it - I think maybe for Macs (15 pin) - but the serial port on most Sun systems was also 15 pin (like on my silver SunBlade 1500) - the USB serial dongle I have is 9 pin - but it works with the 15 pin connector on the other end on a Sun box…
I think the 15 pin connector looked exactly the same as the parallel port (lpt1) on most IBM clones - which probably confused the f–k out of a lot of people (me included - sometimes!).
I have stacks of all sorts of dongles - I hardly ever throw sh!t away… they don’t actually take up much space… Except when I realise I need one of them and can’t find it 'cause I have boxes and crates of shit stacked up… I still have console dongles for Sun (now Oracle) T series blades…
It was, but most of the pins are hardly ever used. You can get away with 9 pins, or
even less.
I think you can manage with 2 data lines, 2 control lines, and a ground.
Correct the lpt connection on older IBM style pc use 25 pins but only 4 connected
Sadly the laplink was not for Mac no similar connections they used scii connection or for printers apple talk cables they were round like ps2 keyboard or mice but slightly different
I’m afraid it used more, as there are at least 8 bits to be transferred.
My very-very first “soundcard” for the PC was a custom-built (self made)
R-2R DAC, this was a 8 bit DAC wired to the LPT port data bits.
Some games, such as Gobliiins (my that time favourite)
could use it, I think the appropriate choice for sound device was covox or something like that.
Did not sound very well, but it was in the golden age, we were excited to have a sound from the PC, if it’s any better than the PC speaker
I also had a MOD player/editor (Scream tracker - I start to feel nostalgic ) that worked with it. We had a huge collection of musics stolen borrowed from an Amiga 500, those sounded just right on that device.
Oh, yes, I found the pinout:
I agree, these connectors were really robust, when fixed the plug with the screws, it was impossible to tear it out!
Only problem was some software used to trace the network and if it found a second cooy of the same software registration it blocked the second version. I learned that, the uni bought one copy of an adobe product instead of 10, one for each machine, admin error of course not cost saving ! So to run the network we had to unplug everyone, just plug them in to print. Then wait till the copies of each machine version arrived to re install and put new licence number in. Yes they provided floppy disks for each machine and version. Before site licence. Good job we got education discount but then needed a big box to store all the discs in.
Great thing about mods - is - you could play them on the PC speaker - didn’t need a soundcard… First one I remember hearing was a mod of New Order’s “Blue Monday”…
I remember someone wrote a “driver” to let you use the PC speaker from Windows - but it ate CPU - some morons would install it and then complain their PC was too slow… I was forever removing that PC Speaker driver from Windows 3.1 and 3.11 machines…
Back in the 70’s and 80’s we use to get new car tags every couple of years. One year, I thought is was very much of a coincidence that I was working in IT and received this car tag.
) that worked with it. We had a huge collection of musics 
