Using PeekNamedPipe?

From:

=?Utf-8?B?UmF5IE1pdGNoZWxs?= <RayMitchell_NOSPAM_@MeanOldTeacher.com>

Newsgroups:

microsoft.public.vc.language

Date:

Sun, 13 Aug 2006 03:18:01 -0700

Message-ID:

<FA8D0083-F07B-4888-BC45-001C56BB52B7@microsoft.com>

Hello,

VS 2003.NET
WinXP SP2

I've got a C console application that sends and receives data through my
PC's COM port 1. When I use just ReadFile and WriteFile everything works
fine. However, I need to be able to check if there is really any data
available before I read it, so it seemed that PeekNamedPipe would be the
appropriate approach. However it always indicates that there are many
characters available. I know it's probably something simple. Here's how
what I think are the important parts of the code look. Nothing is actually
coming into the COM port and all my program does is check it:

HANDLE InitSerialPort(const char *comPort, int baudRate);

HANDLE hComm;

int main(void)
{
   char inCh;
   DWORD dwRead;
   DWORD dwBytesRead;
   DWORD dwTotalBytesAvail;
   DWORD dwBytesLeftThisMessage;

   InitSerialPort("COM1", CBR_115200);

   for (;;)
      PeekNamedPipe(hComm, &inCh, (DWORD)1, &dwBytesRead,
&dwTotalBytesAvail, &dwBytesLeftThisMessage);

   return 0;
}

HANDLE InitSerialPort(const char *comPort, int baudRate)
{
   COMMTIMEOUTS comTimeOut;
   DCB dcb = {0};

   // Open the com port
   hComm = CreateFile(comPort, GENERIC_READ | GENERIC_WRITE, 0, NULL,
      OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
   if (hComm == INVALID_HANDLE_VALUE)
   {
      DWORD errorCode = GetLastError();
      printf("SYSTEM ERROR code 0x%x opening PC %s\r\n", errorCode, comPort);
      exit(EXIT_FAILURE);
   }

   comTimeOut.ReadIntervalTimeout = MAXDWORD;
   comTimeOut.ReadTotalTimeoutMultiplier = 0;
   comTimeOut.ReadTotalTimeoutConstant = 0;
   comTimeOut.WriteTotalTimeoutMultiplier = 0;
   comTimeOut.WriteTotalTimeoutConstant = 0;
   SetCommTimeouts(hComm, &comTimeOut);

   dcb.DCBlength = sizeof(dcb);
   GetCommState(hComm, &dcb);
   dcb.BaudRate = (DWORD)baudRate;
   dcb.ByteSize = 8;
   dcb.StopBits = ONESTOPBIT;
   dcb.fParity = 0;
   dcb.Parity = NOPARITY;
   dcb.fBinary = 1;
   dcb.fRtsControl = RTS_CONTROL_DISABLE;
   dcb.fDtrControl = DTR_CONTROL_DISABLE;
   SetCommState(hComm, &dcb);

   return hComm;
}

Thanks,
Ray