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Most laptops do not have a 9-pin serial port.  So we are forced to use USB to Serial converters or adapters for communicating with devices over RS-232.  Most older GUI software only allows the selection of the lower numbered com ports, such as COM1, COM2, COM3, and COM4.  Often, the drivers for USB adapters are configured to use COM5 and up by default.  In these cases, the GUI will not allow selecting the com port needed to communicate with the hardware device.  And the only way to solve this problem is by changing the com port number of the USB adapter driver.