用分析文件的方法对pcap文件进行解包，pcap文件是tcpdump的标准文件；如果用libpcap开发，要用p_open_offline函数。样例代码，供学习，欢迎指正。-Analysis of documents on file pcap unpack, pcap file is the standard document tcpdump If libpcap development, use p_open_offline function. Sample code for learnin