Background:
I've searched for a good communication class for a while and could not find one.
That's when I decided to write my own and it should be one that's easy to use.

In the newgroups there are many questions about serial communication so I thought:
make it public! It's freeware. The only thing I expect from users is that they drop me a mail.
All modifications on this class are free, but please let me know if it solvers a bug
or adds some good features. Also comment your code and don't let me solve your bugs!

Target:

The class is not intended to use as a baseclass for modemcommunication but
more for driving hardware or reading hardware via the serial port. 

From the classes included there is only one class important: CSerialPort.
The other classes are only there to illustrate the use of this class.

Usage:

In your software you only need to create an instance of the CSerialPort class
and call InitPort.

BOOL CSerialPort::InitPort(CWnd* pPortOwner,		// the owner (CWnd) of the port (receives message)
						   UINT  portnr,			// portnumber (1..4)
						   UINT  baud,				// baudrate
						   char  parity,			// parity 
						   UINT  databits,			// databits 
						   UINT  stopbits,			// stopbits 
						   DWORD dwCommEvents,		// EV_RXCHAR, EV_CTS etc
						   UINT  writebuffersize)	// size of the writebuffer

The dwCommEvents flag can be used for communication with the owner of this class.

The flags can be one of the following (or combined with |):
WM_COMM_BREAK_DETECTED	A break was detected on input.
WM_COMM_CTS_DETECTED		The CTS (clear-to-send) signal changed state. 
WM_COMM_DSR_DETECTED		The DSR (data-set-ready) signal changed state. 
WM_COMM_ERR_DETECTED		A line-status error occurred. Line-status errors are 					CE_FRAME, CE_OVERRUN, and CE_RXPARITY. 
WM_COMM_RING_DETECTED		A ring indicator was detected. 
WM_COMM_RLSD_DETECTED		The RLSD (receive-line-signal-detect) signal changed state. 
WM_COMM_RXCHAR			A character was received and placed in the input buffer. 
WM_COMM_RXFLAG_DETECTED	The event character was received and placed in the input 
					buffer.  

Accept the first parameter all parameters are optional. The standard values are:

portnr		= 1
baud		= 19200
parity		= 'N'
databits		= 8, 
stopsbits	= 1, 
dwCommEvents	= EV_RXCHAR | EV_CTS,
nBufferSize	= 512);

So the follwing code is enough to make communication possible:

in the header of the owner:
	CSerialPort	m_Serial;

in the code:
	m_Serial.InitPort(this);
	m_Serial.StartMonitoring();

Then the tread that watches the port is started and all events on the port are send to
the owner. The receive a character the owner needs a messageentry in the messagemap:

BEGIN_MESSAGE_MAP(CCommtestDlg, CDialog)
	//{{AFX_MSG_MAP(CCommtestDlg)
	ON_MESSAGE(WM_COMM_RXCHAR, OnCommunication)
	ON_MESSAGE(WM_COMM_CTS_DETECTED, OnCTSDetected)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

and they must be handled:

LONG CCommtestDlg::OnCommunication(WPARAM ch, LPARAM port)
{
	// do something with the received character

	return 0;
}

This is it for reading. Writing can be done with WriteChar or WriteToPort

IMPLEMENT_DYNAMIC(CAddItemDlg, CDialog)
CAddItemDlg::CAddItemDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CAddItemDlg::IDD, pParent)
{
}

CAddItemDlg::~CAddItemDlg()
{

}

void CAddItemDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
}

BEGIN_MESSAGE_MAP(CAddItemDlg, CDialog)
	ON_MESSAGE(WM_COMM_RXCHAR, AddItemOnCommunication) //handler 
END_MESSAGE_MAP()

BOOL CAddItemDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	// init the ports
	if (m_Ports[0].InitPort(this, 1, 9600, 'N',8,1,EV_RXCHAR,512))
	m_Ports[0].StartMonitoring(); //Start monitoring the comports, sameway i did in main class, but i stop it before i call this dialog

	
	return TRUE;  // return TRUE unless you set the focus to a control
	// EXCEPTION: OCX Property Pages should return FALSE
}


//CAddItemDlg message handlers

//event if BarCode scans, but the function never reacts or it reacts only once when the monitoring in the main dialog is never called.
LONG CAddItemDlg::AddItemOnCommunication(WPARAM ch, LPARAM port)
{
	if (ch == 13)
	{    
		SetDlgItemText(IDC_BARCODE,m_strReceived[port-1]);
		(m_strReceived[port-1]).Empty();  //clear string
		
//	if (exist==true) //show message box if articel is not found in database
//		MessageBox("Verkaufsartikel schon in Datenbank.", "ALREADY EXISTS",MB_ICONWARNING | MB_OK);
	}
	
	if (!((ch == 13)||(ch == 10))) //keep m_strReceived clean from junk sign 10
	{
		m_strReceived[port-1] += (char)ch;
	}
	return 0;
}