View Full Version : Problem with modem in dos window

Terry Porritt
08-09-2002, 11:08 PM
I can talk to my USR external modem in dos from the prompt command line, eg. echo ATDT0867xxxxx >com2, and it responds ok., no problems.

The same command from a dos window in windows and I get an error message "write fault error writing device com2".

The strange thing is that an ISA internal modem I used to have worked from a dos window.

Ive known about this for some time,but havent bothered about it until trying to run Arachne dos web browser in Windows today.

Anyone any ideas what should be done to get the modem working in a dos window?
(There is no problem with it working from windows, only from a dos window with dos commands).

09-09-2002, 01:53 AM
You don't say what version of Windows you have. XP has no Dos & will not support a modem in a "Dos" window [emulation]. Should work in ME & 98.

Terry Porritt
09-09-2002, 08:54 AM
I'm naughty, should have said OS=Win98SE. (How can anyone use XP without DOS ?:| )

Also should have said the MODE command to query the COM2 port to which the modem is connected gives the same status in both DOS and DOS window, RETRY=NONE.

Graham L
10-09-2002, 06:21 PM
It could be that W98 "owns" I/O devices. This is what "real" OSs do ... user level things aren't supposed to access hardware directly, only through OS routines. In DOS, it's assumed that you own everything. You are at "ring 0".

Terry Porritt
10-09-2002, 06:55 PM
You are probably right Graham, but I cant understand why I was able to use dos commands with my ISA modem in windows. Sometimes it wouldnt hang up in windows so I have a little dos reset program I used to run when that happened.

I've just this moment thought of the windows 'lock' command which is used to get real mode access, maybe that may work.

10-09-2002, 08:56 PM
> I've just this moment thought of the windows 'lock'
> command which is used to get real mode access, maybe
> that may work.

What was the result?


Terry Porritt
10-09-2002, 09:30 PM
No it didnt work Mike, because "lock" is used for direct disk access, like for running undelete which windows won't normally let you do.
Back to the drawing board :)

10-09-2002, 10:48 PM
I was just thinking about a possible next step for this, and wondering whether Windows would let you do what you want to do if you are running DOS in a virtual PC through something like VMWare that JM was talking about the other day.


11-09-2002, 12:06 AM
VM Ware allows several different methods with Network Adapters.

Bridged: Connected directly to the physical network
NAT: Used to share the host's IP address
Host-only: A private network shared with the host
Custom: Specific virtual network

There would almost certainly be a nicer way to do it though.