Subj : Problems with API WriteFile
To   : borland.public.cpp.borlandcpp
From : Jeff Baker
Date : Tue Apr 27 2004 07:16 am

Can someone please point out why this will not work correctly. I think the
WriteFile function is called incorrectly but I can't figure out why. I thank
you in advance.

- Jeff

#include <windows.h>
#include <stdio.h>
#include <conio.h>

void ProgramError(void)
{
   LPVOID lpMsgBuf;
   textcolor(LIGHTRED);

FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM,NULL
,GetLastError(),MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT),(LPTSTR)&lpMsgBuf,0
,NULL);
   cprintf("Program Error: %s",lpMsgBuf);
   cprintf("Press any key to terminate program: ");
   getch();
   exit(EXIT_FAILURE);
}

int main(int argc, char *argv[])
{
   DCB dcb;
   HANDLE hCom;
   BOOL fSuccess;
   int send_stream[]={4,0,0,0,4,0};
   DWORD nNumberOfBytesToWrite;
   LPDWORD lpNumberOfBytesWritten;
   int x;
   char *pcCommPort;
   for (x = 0; x < argc; x++)
   {
      if (strcmpi("COM2",argv[x]) == 0) pcCommPort = "COM2";
      else if (strcmpi("COM3",argv[x]) == 0) pcCommPort = "COM3";
      else if (strcmpi("COM4",argv[x]) == 0) pcCommPort = "COM4";
      else pcCommPort = "COM1";
   }
   hCom =
CreateFile(pcCommPort,GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING,0,NULL
);
   if (hCom == INVALID_HANDLE_VALUE) ProgramError();
   fSuccess = GetCommState(hCom,&dcb);
   if (!fSuccess) ProgramError();
   dcb.BaudRate = CBR_19200;
   dcb.ByteSize = 8;
   dcb.Parity = NOPARITY;
   dcb.StopBits = ONESTOPBIT;
   fSuccess = SetCommState(hCom,&dcb);
   if (!fSuccess) ProgramError();
   textcolor(LIGHTGREEN);
   cprintf("Serial port %s successfully reconfigured\r\n",pcCommPort);
   nNumberOfBytesToWrite = 6;
   lpNumberOfBytesWritten = 0;
   fSuccess =
WriteFile(hCom,send_stream,nNumberOfBytesToWrite,lpNumberOfBytesWritten,NULL
);
   if (fSuccess == 0) ProgramError();
   if (nNumberOfBytesToWrite != *lpNumberOfBytesWritten) ProgramError();
   cprintf("Data stream was send successfully to serial port
%s\r\n",pcCommPort);
   getch();
   exit(EXIT_SUCCESS);
}

.