title: FT_W32_CreateFile Failed
body: <p>I am using FTDI D2XX Programmer's Guide to interact with FTDI serial-to-usb converter. The following code is used to open the USB port. </p>
  
  <pre><code>      bool CUsbPort::OpenIOHandle()
        {
          m_hComm = FT_W32_CreateFile(m_SerialNumberBuf,
          GENERIC_READ | GENERIC_WRITE,
          0,
          0,
          OPEN_EXISTING, 
          FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED |         FT_OPEN_BY_SERIAL_NUMBER,
          0);
          return m_hComm == INVALID_HANDLE_VALUE ? false : true ;
       }
  </code></pre>
  
  <p>We have a service application to open the port every 5 or 10 minutes to read from and write to our devices. This is a multi-threaded application. I may have more than two devices connected to this application at the same time. When the application runs overnight, I observed there are several cases where FT_W32_CreateFile function failed for all of the threads. Then, they worked again. There may be 2 or 3 times in a overnight run.
  I want to know what conditions may cause the function failing.
  Thanks in advance.</p>