C / C++ / MFC

class COMPort
{
public:
   COMPort() {
     m_bOpened=FALSE;
     m_hCom=INVALID_HANDLE_VALUE;
   }
   ~COMPort() {
     if ( m_hCom != INVALID_HANDLE_VALUE ) {
       CloseHandle(m_hCom);
     }
   }
   BOOL OpenSerialPort();
public:
   BOOL m_bOpened;
   HANDLE m_hCom;
};

COMPort::OpenSerialPort()
{
	if(!m_bOpened)
	{
		DCB    dcb;
		BOOL   fSuccess;
		COMMTIMEOUTS CommTimeouts;
		
		m_hCom = CreateFile("COM2", 
			GENERIC_READ | GENERIC_WRITE, 
			0, NULL, 
			OPEN_EXISTING,
			0, NULL);
		
		if(m_hCom == INVALID_HANDLE_VALUE)
		{
//			AtlTrace("Opening Serial Port Failed");
			return FALSE;
		} 
		
		fSuccess = GetCommState(m_hCom, &dcb);
		if(!fSuccess) 
		{
//			AtlTrace("GetCommState failed with error %d.\n", GetLastError());
			return FALSE;
		}
		
		dcb.BaudRate        = CBR_57600;   // set the baud rate
		dcb.ByteSize        = 8;           // data size, xmit, and rcv
		dcb.Parity          = NOPARITY;    // no parity bit
		dcb.StopBits        = ONESTOPBIT;  // one stop bit
		dcb.fBinary         = TRUE;
		dcb.fOutxCtsFlow    = FALSE;
		dcb.fOutxDsrFlow    = FALSE;
		dcb.fDsrSensitivity = FALSE;
		dcb.fOutX           = FALSE;
		dcb.fInX            = FALSE;
		dcb.fParity         = FALSE;
		dcb.fNull           = FALSE;
		dcb.fRtsControl     = RTS_CONTROL_DISABLE;
		dcb.fAbortOnError   = FALSE;
		
		fSuccess = SetCommState(m_hCom, &dcb);
		if(!fSuccess) 
		{
//			AtlTrace("SetCommState failed with error %d.\n", GetLastError());
			return FALSE;
		}
		
		GetCommTimeouts(m_hCom, &CommTimeouts);
		CommTimeouts.ReadIntervalTimeout = 20;
		CommTimeouts.ReadTotalTimeoutMultiplier = 20;
		CommTimeouts.WriteTotalTimeoutMultiplier = 0;
		CommTimeouts.WriteTotalTimeoutConstant = 100;
		fSuccess = SetCommTimeouts(m_hCom, &CommTimeouts);
		if(!fSuccess)
		{
//			AtlTrace("SetCommTimeouts failed");
			return FALSE;
		}
		
		PurgeComm(m_hCom, PURGE_TXABORT | PURGE_RXABORT);
		
		m_bOpened = TRUE; 
	}	
	return m_bOpened;
}

COMPort::SomeMemberFunction()
{
   DWORD num;
   unsigned char data[10];
   if(m_bOpened) ReadFile(m_hCom, &data[0], 1, &num, NULL);
}