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DOS Printer redirection

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First post, by zerker

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So I found out the DOS MODE command allows you to theoretically redirect a parallel port to a serial port. This is potentially great, as I can just capture the serial output on another machine via null modem and save formatted print output to disk.

Trouble is, it doesn't seem to work. I initially run the command and the output looks promising:

> mode lpt1=com1

LPT1: rerouted to COM1:

But as soon as I check the general mode status again, it says it isn't redirected after all.

> mode

Status for device LPT1:
-----------------------
LPT1: not rerouted
Retry=NONE

Code page operation not supported on this device

Status for device LPT2:
-----------------------
LPT2: not rerouted

Status for device LPT3:
-----------------------
LPT3: not rerouted

Status for device CON:
----------------------

Code page operation not supported on this device

Status for device COM1:
-----------------------
Retry=NONE

If I try to print via MS DOS Edit, or manually redirect a command output to LPT1, it fails just as before. Redirecting a file to COM1, or using a program with serial printing (MS DOS Help) works as usual. I do, of course, already have the mode configured properly for COM1 itself.

I'm running official MS-DOS 6.0. Any thoughts or suggestions? Anyone else tried this sort of thing?

Reply 1 of 5, by Jo22

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Hi, running DOSV 6.20 here and it works fine so far. ^^

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"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 3 of 5, by Jo22

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Hi, did you try mode lpt1:=com1: (with colons), too ?

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 4 of 5, by zerker

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I just tried it in a VM, with the same command I originally used, and it works there. Next step is to check if my serial port settings are causing the problem. Maybe 19200 baud is too fast to permit redirection?

EDIT: And did a bit more testing on my real machine. Didn't have any more luck than before with 9600 baud, or with colons in the ports. I noticed one difference from the VM, it printed the message:
"Resident portion of MODE loaded"
which is not printed on my real machine at all.

I've tried with a bare-bones configuration to essentially match the VM's fresh install, but no change with that either. Finally, I tried disabling the real parallel port in the BIOS (since nothing is connected), but that made no difference.

Reply 5 of 5, by Jo22

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Sorry to hear. 🙁 My copy of DOS holds MODE in memory. It consumes about 480 bytes of memory.
Maybe I'll check again as soon as I have access to a real DOS machine again.

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"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

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