serial communication (cseral class with handshaking control)

DTR/DSR handshaking is used because this is what the POS printer requires. Comms with a pc can then be accomplished using the same cable as used for the printer. Ensure that the pc program is written to use the same handshaking.

我自己写的串口接受程序，可以接受串口程序。-This program was writed by myself,it can be used as serial communication.

this file is very imporant,