Vérifier si un port com est accessible

{Port: COM1, COM2, COM3...}

function ComPortAvailable(Port: PChar): boolean;
var
DeviceName: array[0..80] of Char;
ComFile: THandle;
begin
StrPCopy(DeviceName, Port);

ComFile := CreateFile(DeviceName, GENERIC_READ or GENERIC_WRITE, 0, nil,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL, 0);

Result := ComFile <> INVALID_HANDLE_VALUE;
CloseHandle(ComFile);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
if ComPortAvailable('COM1:') then
ShowMessage('Port available')
else
ShowMessage('Port not available');
end;