cb-dos networking

cb-dos images a vintage machine's disk to a file over BIOS int 13h. To get that file off the machine without shuffling floppies, the cb-dos CD can carry a small DOS TCP/IP stack — mTCP (GPLv3, by Michael Brutman) — so you can FTP the backup to another PC. This page is the user guide and the packet-driver reference.

The two pieces you need

DOS networking is always two layers:

1. A packet driver — a tiny TSR (.COM) specific to your network card. It talks to the NIC and exposes it on a software interrupt (we use 0x60). There is no universal driver, but the media now bundles the Crynwr GPL collection (~90 drivers): the CD carries the full set under \NET\DRIVERS, and the floppy a common subset (NE2000, NE1000, PCNTPK, RTSPKT, 3C509, 3C503, SMC_WD, E100BPKT). The card → driver map is in ../crusty-backup/net/drivers/DRIVERS.TXT (also at \NET\DRIVERS\DRIVERS.TXT); if your card is not covered, drop its .COM into net/drivers/ (refresh the set with net/fetch-drivers.sh) and rebuild.
2. mTCP — the TCP/IP applications (DHCP, FTP, FTPSRV, PING, …) that run on top of the packet driver.

Quick start on the booted DOS box

The CD mounts as a drive letter (typically D: — the FreeDOS boot floppy loads a CD-ROM driver). Then:

REM 1. Load YOUR card's packet driver on software int 60h (see DRIVERS.TXT).
REM    NE2000 clone at I/O 300h, IRQ 3:
D:\NET\DRIVERS\NE2000 0x60 3 0x300

REM 2. Get an IP and see what's next:
D:\NET\NET

REM 3a. Serve the backup so another PC pulls it (easiest):
D:\NET\FTPSRV
REM    ...then from your modern PC:  ftp <dos-box-ip>   (log in, `get backup.img`)

REM 3b. ...or push it out to an FTP server:
D:\NET\FTP <server>      (log in, `put backup.img`)

\NET\NET.BAT sets MTCPCFG=\NET\MTCP.CFG and runs DHCP for you; tweak MTCP.CFG for a static address. Copy \NET to a writable disk first if you want to keep DHCP's leased settings between runs.

No network card? Use a serial cable (SLIP)

mTCP speaks SLIP over a COM port, so any machine with a serial port can transfer over a null-modem cable to a host running a SLIP peer — slow, but it needs no NIC and no packet driver. See the mTCP PDF (EtherSLIP) bundled with the apps.

The packet-driver "library"

We can't bundle every driver (they're per-card and come from card vendors / the GPL Crynwr collection), so the repo ships the map and you drop in the one(s) you need:

Card / chipset	Packet driver	Notes
NE2000 / RTL8019 (ISA)	NE2000.COM	the workhorse; NE2000 0x60 <irq> <io>
3Com 3C509 (ISA)	3C5X9PD.COM	self-configuring
3Com 3C905 (PCI)	3C90XPD.COM
AMD PCnet (ISA/PCI)	PCNTPK.COM	common in emulators/qemu too
Intel EtherExpress Pro/100	E100BPKT.COM
DEC 21x4x "Tulip" (PCI)	DC21X4.COM
Realtek 8139 / 8169 (PCI)	RTSPKT.COM / R8169PD.COM
SMC/WD 80x3 (ISA)	WD8003E.COM
DM&P Vortex86 R6040 (ITX-Llama)	vendor DOS packet driver	from DM&P

Get drivers from the card's driver disk/vendor site, the Crynwr packet driver collection (GPL; mirrored on DOS archives and the Internet Archive — look for PKTD11.ZIP), or the FreeDOS networking packages.

Building media with networking

There are two networking lanes, and they ship differently:

• crustybk's own backup rb://host/name (the WATT-32 stack baked into CRUSTYBK.EXE) works from both the floppy and the CD. The floppy carries WATTCP.CFG (DHCP by default) at its root and a \NET\DRIVERS directory; drop your card's packet driver into net/drivers/ and it lands there. (To fit the ~1 MB networked CRUSTYBK.EXE on a 1.44 MB floppy, mkmedia.sh UPX-packs it — it self-extracts into RAM at launch, so the stack is fully intact.)
• The mTCP FTP suite (move a finished backup file off the box over FTP) is larger and rides the CD only:

sh crusty-backup/net/fetch-mtcp.sh                 # download mTCP (GPLv3), once
cp /path/to/NE2000.COM crusty-backup/net/drivers/  # your card's packet driver(s)
FDBASE=/path/to/x86BOOT.img sh crusty-backup/mkmedia.sh

mkmedia.sh adds a \NET directory (mTCP apps + your packet drivers + MTCP.CFG + NET.BAT) to cbdos.iso when net/mtcp/ is populated; without it the CD's mTCP lane is absent (the floppy's \NET\DRIVERS + WATTCP.CFG for backup rb:// are always present). Repo-side layout: ../crusty-backup/net/README.md.

Status / caveats

• This is the transport for backups (FTP), not an integration into cb-dos's imaging — image to a file, then FTP it. A future step could stream directly.
• Accessing \NET assumes the boot environment loaded a CD-ROM driver (the FreeDOS 1.4 boot floppy does); if not, copy \NET from the CD by hand.
• Not yet tested on real hardware with a real NIC — the build wiring is in place; the DOS-side walkthrough above follows standard mTCP usage.
• mTCP needs ~96–256 KB free RAM depending on the app; fine on anything that runs DOS networking at all.