PPP拨号上网协议栈，通过串口编程，实现PPP拨号网络底层协议以及TCP/IP协议，主要用于GPRS，CDMA，电话拨号等通信领域。-PPP dial-up Internet protocol stack, through serial programming, PPP dial-up network to achieve agreement and the underlying TCP/IP protocol, mainly for GPRS, CDMA, such as dial-up te