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### Connecting a no-NIC 8086 PC to LAN through its parallel port ### Here's the story: I'm the lucky owner of an ancient Toshiba T1100 laptop. This laptop is fitted with an 80C86 CPU, 256 KB of RAM, two floppy drives and no Ethernet port. There is also no way to add an Ethernet adapter. Since the computer doesn't have a hard disk, working on it can get slightly frustrating sometimes (swapping those 720K floppies all the time is fun, but come on). I dreamed about being able to connect this laptop to a big network drive where I could store all my relevant stuff, so the floppy drive would be used only for booting DOS. As a network drive solution, I use EtherDFS. Problem is, I need to connect somehow the Toshiba T1100 to my Ethernet LAN, and without an Ethernet adapter, it's no trivial task. *** PLIP *** PLIP stands for "Parallel Line Internet Protocol". It's a protocol that allows to send and receive packets through the parallel (LPT) port of a computer. While the name suggests it operates at the layer 3 (IP) level, nothing could be less true. PLIP is actually Ethernet-aware, meaning it sends and receives full Ethernet frames. And that's perfect for what I needed to do. *** The PLIP client *** Russ Nelson from Crynwr wrote a PLIP packet driver for DOS. It's a network packet driver that emulates an Ethernet card, and sends/receives frames through the computer's parallel port. Its usage is pretty straight-forward, assuming one knows what IRQ and I/O port the local parallel port runs at: plip -c 0x60 7 0x378 54:52:00:11:22:33 Note: the PLIP packet driver is able to auto-detect the I/O port and IRQ of the LPT port on newer computers (it did so splendidly on my 386SX), but apparently not on 8086-class computers, where it requires those to be passed as arguments. *** The PLIP "server" *** Okay, I have my brave 8086 computer sending Ethernet frames through its parallel port, but what next? I still need to hook somehow its parallel port to my Ethernet LAN. This is where the server part comes in. I thought, "wouldn't it be convenient to have some sort of switch that could have some Ethernet ports and a PLIP access port?". Obviously such hardware contraption doesn't exist (or at least I am not aware of this), but still, there is a solution: use another PC as a switch! There is this YAPCBR project from the university of Bombay that does exactly what I needed: it turns a DOS PC into a switch, operating on packet drivers running on said PC. YAPCBR stands for "Yet Another PC BRidge", presumably in reference to the "PCBRIDGE" tool that does a similar thing (I did not test PCBRIDGE, in my understanding it operates directly on network cards, while I needed a solution that talks to packet drivers). Now, all I had to do was to start my 386SX desktop PC (whose Ethernet card is connected to my LAN already), load the PLIP packet driver additionally to the packet driver related to the 386SX's Ethernet network card, and finally execute YAPCBR. The latter made sure to forward Ethernet frames between my 386SX's network card and the PLIP packet driver back and forth. Naturally, for the whole trick to work, both computers had to be connected together with a parallel cable (same kind as used for LapLink-style parallel transfers). +---------------+ +--------------+ | TOSHIBA T1100 | | 386 SX | | | Parallel cable | | | LPT :--------------------: LPT ETH :--------> MY LAN | | | | | PLIP pkt drvr | | <- YAPCBR -> | +---------------+ +--------------+ The 386SX PC acts as a dual port switch. Once all this was set, I could enjoy having Ethernet connectivity on my Toshiba T1100 laptop, meaning the EtherDFS network drive solution was able to load. From now on I could access my multi-gigabytes network drive without having to transfer files on diskettes. Of course having to transform another PC into a PLIP switch isn't very convenient. A more elegant solution would be to use a hardware "PLIP to Ethernet" device, and it would appear that such device actually exists: it's called "plipbox" and it's an open-hardware project from Chris (aka "Lallafa"). Plipbox is designed to provide Ethernet connectivity to Amiga computers, but I suppose it would work just as well with a PC. I did not follow this path though, since I'm already very happy with the YAPCBR solution. If you're curious about Lallafa's plipbox, read more about it on Chris' website at http://lallafa.de/blog/amiga-projects/plipbox/. Another solution could be to buy a Xircom PE3-10BT adapter - it's basically an Ethernet adapter connected to the LPT port, produced by Xircom during the nineties (and increasingly hard to find nowadays). === Attachments ========================================== BIN plip112.zip BIN ypcbr102.zip