1. The default port of the invoice system is the printer driver, which depends on the port of your printer properties;

2. There will be no problem with the lpt port of the general printer. After installing the driver, are you sure you want to print a test page? There is something wrong with the onboard lpt port on some computer motherboards. You can try another computer;

3. It is better to use lpt port in the invoice system, which is relatively stable. You can also use usb. If you use a usb interface, you should select usb 1 in the port settings of the printer properties. ..