What USB to serial adapter are you using? I deal with this a lot at work because we need to connect to serial ports on a lot of legacy devices.
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Here is the adapter I have found to work the best
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This assume your scanner used a DB9 connector youll need an appropriate adapter to go from what ever the scanner uses to the db9. Also you may need to order a null modem cable but you need to find the manual for the gear to know for sure.
Also when you use a USB to serial converter Windows will assign it a virtual serial port number you need to go into device manager and see what com port your adapter is given usually but not always it start at com 3
Than you need to get your software to attempt the connection using the assigned com port or alternatively use device manager to override the com port assignment and change it to 1 and see if that helps.
This should work but you will need a gender bender
Can't seem to find the cable that I have though.