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Network over RS-232

Ruud

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In another thread I made a remark about creating a network over RS-232. And that popped up the memory that I have seen such a network around 1988. IIRC it was just a card with at least two 9-pin D-connectors (male, female, or a mix?) and its own 16450 (or two?). Does that ring a bell?

The main reason that I'm asking is pure curiosity. But it is vintage and being a tinkerer with old PCs, maybe, maybe it is possible to recreate it in one or another way.

Thanks in advance for any info or pointer!
 

Plasma

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There were token ring NICs with DB9 connectors, but they were not RS232.

If you have two RS232 ports on each computer and null modem cables, I suppose you could roll your own token ring RS232 network. But you would have to write the software.

If the computers have parallel ports, Xircom PE3, Plipbox, etc would be a better choice.
 

jdreesen

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Not what you are talking about, but there was Econet and Omninet, amongst others. I recently tried out Omninet on 2 DOS PC's and was impressed by its usability. Both networks use a serial protocols running on a a MC6854.
 

Timo W.

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IIRC it was just a card with at least two 9-pin D-connectors (male, female, or a mix?) and its own 16450 (or two?). Does that ring a bell?
Sounds like Artisoft LANtastic. I still own such a card. 8-bit ISA with two DB9 connectors (one male, one female). Though the card I have is powered by a Z80.
 
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daver2

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Not specifically Commodore - but at our computer meetings (many, many years ago...) we just strung a few uninsulated copper wires around the tables and people connected their computer serial ports up to the copper wires using crocodile clips. Not that we shared software or anything like that using this mechanism. of course...

However, this was a 'bespoke' serial protocol.

I remember a few people had some Commodore equipment (I was somewhat envious at the time)...

Dave
 

Ruud

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Sounds like Artisoft LANtastic. I still own such a card. 8-bit ISA with two DB9 connectors (one male, one female). Though the card I have is powered by a Z80.
That sure does ring a bell. I have tried some googling but didn't find anything. Thank you anyway!

But during that googling I ran into a card with multiple COM ports meant to be used in a Xenix server. That triggered an idea: I have an ISA card at home with eight (?) ports. By coincidence I have prepared a Pentium-II with ISA slots last week for another project and with this card it could serve as a kind of local network server. And now I only have to find some time.......
 

RussBlakeman

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Sounds like Artisoft LANtastic. I still own such a card. 8-bit ISA with two DB9 connectors (one male, one female). Though the card I have is powered by a Z80.
Yep LANtastic came in two versions that I remember, a serial version and a thinnet coax version that used (IIRC) 3.5mm phone plugs. I had the thinnet version between two 286 PCs in the late 80s or early 90s and my sons and I would play the network version of Doom through it. I don't have the kit anymore (I thin I sold it on eBay when it was a new marketplace) but it came with a length of coax, two NICs and software on 3.5" floppies. After that I went to thinnet using coax that had BNC connectors. I may still have some of those BNC ISA NICs stashed in a box somewhere. The coax was repurposed for test equipment use since.
 

mbbrutman

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RS232 is point to point, so it's hard to get a network out of that.

However, if you had a group of machines that each had two RS232 ports then you would be able to construct a sophisticated, but slow network. If a machine receives a message that is not for it, then it passes the message down the line on the other port. Which is basically the way Token Ring works. (Yes, I know, a gross simplification ...)
 

daver2

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Nope, you can multidrop RS232 - providing you use diodes in the transmit lines all of all the participants and you ensure that only one computer is 'transmitting' at any one time :).

Cheap and very nasty...

Dave
 

krebizfan

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There were a number of European computers that split a single serial port into two DIN connectors to create a daisy chain network. IIRC, the Elwro 800 from Poland had an educational version using Junet and a later version that replaced the two DIN connectors with a single standard RS-232 port with corresponding changes to the firmware. Doing the same with two serial ports just costs more.
 

Svenska

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According to some Xenix-286 documentation I found, Xenix (probably all versions) supported "Micnet". It was run over RS232, and machines could be daisy-chained or configured as hub/router. Each machine had to know the whole network topology. Never saw technical documentation about it, though.
 

Eudimorphodon

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Nope, you can multidrop RS232 - providing you use diodes in the transmit lines all of all the participants and you ensure that only one computer is 'transmitting' at any one time :).

Cheap and very nasty...

This is what RS-422 was really good at. Apple built the "Localtalk" networking standard around the RS-422 support in the Zilog SCC serial chip they chose for the Macintosh, which was probably the single best hardware feature of the machine. There were various PC implementations of RS-422 network hardware, usually with various levels of interoperability with Apple's version; maybe the best known one was TOPS.

But, yeah, this is neither here nor there when it comes to networking over standard PC serial ports. One strategy which avoids having to have a server with a gazillion serial ports is doing a "ring" topology where the transmit lines of one computer's serial port go to another PC's input lines, and that machine's output goes to the input of *another* computer, and so forth, until the last computer in the ring feeds back to the first one. In that setup each computer plays "telephone" for data packets not destined for it, just passing them around the ring to the next node. This method means you only need one serial port per PC, but the obvious downside is that if any of the machines goes out to lunch the whole network breaks.
 

Eudimorphodon

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Don't overlook ComRing. This was a late entry (~1996 -> 1998) and more of a hobbyist system that could network up to four computers through one serial port per computer using special "null-modem cables." It also was free, IIRC, and the source is available:

This is a perfect poster child for the "ring" topology I mentioned. Again, it can totally work, but if one of the computers stops listening the whole house of cards goes down.

What makes this less good than a "real" ring topology network is there's no hardware on the PC UART to offload any of the link layer functions, like error checking or determining whether a given packet of data is for "you" or if it should just be passed down the line. The CPU has to handle all of it, and if you end up with an overrun or data link error the handshaking has to waddle all the way around the ring again. (And again, could get messed up by another computer not being quick enough on the draw.)
 

Eudimorphodon

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If you really wanted to suffer it might be entertaining to use a Linux machine with some arbitrary number of USB serial dongles hanging off it as the "server" for a pile of SLIP/PPP host connections and then run whatever kind of packet driver-compatible network protocol over the top of that. USB serial dongles and a hub are cheap, most OSes have some kind of SLIP/PPP driver available, you can have it all this way. FTP, telnet, even NFS, the world is your oyster. Your slow, slow, so painfully slow-ouch-it-hurts-don't-touch-it oyster.
 

krebizfan

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With some of the simpler serial port networks, the upstream and downstream ports were wired together and the signal will propagate even through a rebooted or off machine.
 

twolazy

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Why not try a ESP8266 and use wifi over serial. That should allow you to at least use ftp over serial, would that be good enough? I believe SLIP/PPP works as well.

 

bladamson

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Back in high school I daisy-chained a bunch of PS/2 Model 25s together with null-modem cables and wrote software to exchange messages between nodes. It was pretty simple and inefficient, lol. Just sent the packet over both ports, to both of the next links in the chain. If it the recipient saw that the packet was addressed to it, it consumed the packet, otherwise it just forwarded it through the other port.

The idea was to make a multiplayer dungeon crawl game with it, but I never got that part done..... Lol.

This was all in qbasic, too. D:
 
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