/* Open device */
    hDevice =
        CreateFileA( pszDev,
                     dwDesiredAccess,
                     0 /* dwShareMode: must be zero (exclusive access) for COM port according to MSDN */,
                     NULL,
                     OPEN_EXISTING,
                     0,
                     NULL );

    free( pszDev );

    if( hDevice==INVALID_HANDLE_VALUE )
// тут был их возврат     return fb_ErrorSetNum( FB_RTERROR_FILENOTFOUND );, но мы продолжим
    {
        DWORD dwError = GetLastError();
        if(dwError == ERROR_ACCESS_DENIED || dwError == ERROR_GEN_FAILURE)
            return fb_ErrorSetNum( Какая-то константа ошибки );
    }                          

    return fb_ErrorSetNum( FB_RTERROR_FILENOTFOUND );

      #BUFFERSIZE = 128
      #MAX_SERIAL = 255
      
      Protected Buffer${#BUFFERSIZE}
      Protected i
      
      For i = 1 To #MAX_SERIAL
        If QueryDosDevice_("COM"+i, @Buffer$, #BUFFERSIZE)>0
          AddGadgetItem(#Port, -1, "COM"+i)
        EndIf
      Next

#SerialPort=0
sp.s

port = ExamineDirectory(#PB_Any, "/dev/", "*.*")
If port
  While NextDirectoryEntry(port)
    If DirectoryEntryType(port) = #PB_DirectoryEntry_File
      sp = DirectoryEntryName(port)
      If FindString(sp, "tty", 1, #PB_String_NoCase) = 1
        If OpenSerialPort(#SerialPort, "/dev/"+sp, 9600, #PB_SerialPort_NoParity, 8, 1,  #PB_SerialPort_NoHandshake, 1024, 1024)
          CloseSerialPort(#SerialPort)
          AddGadgetItem(#Port, -1, sp)
        EndIf
      EndIf
    EndIf
  Wend
  FinishDirectory(port)
EndIf