实现截获gmail数据包（非端口过滤手段），并且显示其头部特征字-Gmail to achieve intercept data packets, and shows characteristics of the head word

CRC即循环冗余校验码（Cyclic Redundancy Check）：是数据通信领域中最常用的一种差错校验码，其特征是信息字段和校验字段的长度可以任意选定。-The cyclic redundancy check code CRC (Cyclic Redundancy Check): A data communications of the most commonly used error check code, characterized in that the information f