来自：http://www.codeproject.com/Articles/382/CSerialPort-v-Serial-Port-Wrapper

Features

• Simple and clean C++ interface.
• Uses C++ exceptions in preference to the normal Win32 return value mechanism. This ensures that code which uses CSerialPort is more robust.
• Unicode enabled, supports linking to MFC statically and all code compiles cleanly at warning level 4.
• Supports overlapped, blocking and callback usage models of the serial port. (Callback is only supported on NT)

Remarks

This function is called as the completion routine for any asynchronous calls to WriteEx or ReadEx. In your derived class from CSerialPort, you can override this function to perform your own specific code in reaction to an asynchronous call completion. Don't forget to call the parent version, namely this functionCSerialPort::OnCompletion as it handles the cleanup of the memory allocated for the lpOverlappedparameter.