Printer Ports DOT4_001 and USB003

In my software I am blocking printing to a file or any other devices, allowing only real printers?
Most printers are printing to DOT4_001, one of the users send me an email complaining that his printer is not printing from my software. I dicovered that he is printing to port USB003.

I tested it, if the computer has two printers (A) and (B)
If the port for printer (A) is USB003 and changed to DOT4_001 port then printer (B) is receiving the print order.

Why some printers use DOT4_001 and some uses USB003?
is it necessary to have a port for each printer? or
Is there away to make all printers print using DOT4_001? (one port)
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Dave BaldwinFixer of ProblemsCommented:
I have printers assigned to USB001 and USB003.  I have a port named DOT4_001 but there is no printer associated with it anymore.  These are all 'virtual' ports that are assigned by Windows and the driver software.  If you put the USB plug in a different physical port, I think you will see the port name change.

And I don't have any of those ports on the computer on my right because the only computer directly connected is on an old parallel port and not on a USB.

I don't think you can force them all to print to a particular port unless you have a printer connected to that same port on all the computers.
☠ MASQ ☠Commented:
Virtual USB ports are created per print device.  If you had a universal (eg DOT4 virtual port it would behave like a physical port with multiple printers attached & each printer would try to process the job from the printer spool.

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saljasAuthor Commented:
Many thanks for you reply
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