单片机实现的CRC校验，特别针对PPP协议验证过。 多项式是：CRC16-CCITT x16+x12+x5+1

UDP and TCP 可以使用这个文件来运行任何tcp和udp，然后做成后端和前端(The server communicating with the client is called AWS (Amazon Web Server). The three backend servers are named Back-Server A, Back-Server B and Back-Server C. Back-Server A can compute x2 , Back-Server B