实现用串口收发数据，开启串口，采用轮询的方式不断检测是否有串口的数据的到来-Implementation used to send and receive serial data, open the serial port, using polling manner Detect Whether or not there is the advent of serial data

DLL编程，主要涉及了串口控件的使用以及串口通信的实现，同时以DLL的方式调用-DLL programming, mainly related to the use of the serial port control, as well as the realization of serial communication, called the DLL manner