Assuming you are only using Windows you will need to use the registry to get this information.
You can get a list of all COM ports on the system here: HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM
. Values will be listed according to their type, so a real serial port will show up with a name \Device\Serialn and data COMxx, other devices might be different. If you look here you can find a name you can use to filter which type of device a COM port belongs to, then simply list these in your application.
You can do this in Xojo by using the Declare
statement to hook into the API of the Windows DLLs:
https://docs.xojo.com/index.php/Declare
Here is a document on the Registry API functions, they will be used as described here, but using the Declare
statement mentioned above:
http://support.microsoft.com/kb/145679