title: ReadFile() returns a blank data
body: <p>I'm testing serial port communication by connecting COM port RD and TD pins together.
  The COM port has been initialized before the code below is executed.</p>
  
  <pre><code>CString cs_Send = "F: 5000000 Hz, SF: 1.0, Phase: 10, Position: 50, on sample 1";
  
  BOOL bWriteRC = false;
  BOOL bReadRC = false;
  DWORD iBytesWritten = 0;
  char readBuffer[256] = {"\0"};
  
  DWORD read;
  
  bWriteRC = WriteFile(hPort,cs_Send.GetBuffer(10),cs_Send.GetLength(),&amp;iBytesWritten,NULL);
  **Sleep(1000);// Thanks for the advice!!! this Sleep() will fix this error.**
  bReadRC = ReadFile(hPort,readBuffer,sizeof(readBuffer),&amp;read,NULL);
  
  if(bWriteRC)
  {
      if(bReadRC)
      {
          AfxMessageBox(readBuffer, MB_OK);
      }
  }
  </code></pre>
  
  <p>The bWriteRC and bReadRC always return true. But the first message is completely blank. And if I run this more than twice, every message after the 1st is exactly same as what I sent. I wonder why the first one is always blank.</p>