List available COM ports

I have a screen from which users select a COM port. Instead of just listing COM1... COM8 in a listbox, I would like to display available com ports only.
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below is in the MSDN article "Serial Communications in Win32":

                   One thing to note about port names is that traditionally they have
                   been COM1, COM2, COM3, or COM4. The Win32 API does not provide any
                   mechanism for determining what ports exist on a system. Windows NT and
                   Windows 95 keep track of installed ports differently from one another,
                   so any one method would not be portable across all Win32 platforms.
                   Some systems even have more ports than the traditional maximum of
                   four. Hardware vendors and serial-device-driver writers are free to
                   name the ports anything they like. For this reason, it is best that
                   users have the ability to specify the port name they want to use. If a
                   port does not exist, an error will occur (ERROR_FILE_NOT_FOUND) after
                   attempting to open the port, and the user should be notified that the
                   port isn't available.

So that you should enumerate them by checking the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Ports, or

However, in Win95/NT, the location might be slightly different.
alexandramAuthor Commented:
Thank you. I guess I won't bother since my application runs on both 95 and NT.
from the groups (tested on D3, NT4):

procedure TForm1.Button1Click(Sender: TObject);
MaxPortsExpected = 8; // WIN95 max = 9; NT =256
HCom : THandle;
PortNum : integer;
PortName: string;
  for PortNum := 1 to MaxPortsExpected do
   PortName := 'COM'+IntToStr(PortNum);
   hCom := CreateFile(PChar(PortName),
                     GENERIC_READ or GENERIC_WRITE,
    if hCom = INVALID_HANDLE_VALUE then
      ShowMessage( PortName +' : not present, or already in use' )
      GetCommState(hCom, DCB);
      with DCB do begin
          ShowMessage( PortName +' : available'+#13
                     +'Baud:'    + IntToStr(BaudRate) +#13
                     +'ByteSize:'+ IntToStr(ByteSize) +#13
                     + 'Parity :'+ IntToStr(Parity));
      CloseHandle( hCom );


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alexandramAuthor Commented:
Thank you.
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