[wplug] Serial killer

[Vance Kochenderfer]

My parents have been having trouble with their external serial modem.
It reportedly worked fine last Friday, but when they went to go online
Saturday morning, no go.  I've spent a bunch of time with them on the
phone (from a couple hundred miles away) trying to diagnose the trouble,
but have hit a brick wall.  They're using Mandrake 10.1 (kernel 2.6.8).

The modem simply won't respond to commands.  KPPP has a nifty "Query
Modem" function that sends a series of ATI commands to the modem.
This causes the modem lights to flicker, but no response comes back.
Trying an ATZ or any other AT command in a terminal likewise gets no
reply.  I suspected the modem could have died, but I had them put on
an old modem I had left at their house, and we get the same results.

My next suspicion was a serial port problem, but dmesg and a
setserial -a /dev/ttyS0 both show normal values.  Permissions on
/dev/ttyS0 are correct.  There's only one serial port, so I know
it's the right device.  It's properly enabled in the BIOS.

Anyone have any ideas for further diagnosis I can do remotely (with
non-computer literate people on the other end)?  Or alternatively, if
it turns out the serial port is bad, anyone have a PCI modem that
works under Linux they'd like to unload?  Thanks a bunch.

Vance Kochenderfer        |  "Get me out of these ropes and into a
vkochend at nyx.net          |   good belt of Scotch"    -Nick Danger