android app要抓TCP数据包，我们可以使用TCPdump工具！
下载tcpdump，可到http://www.tcpdump.org/查看使用文档.
还有个地址是http://www.strazzere.com/android/tcpdump.
具体步骤：
1.需要root权限
2.推送tcpdump文件到手机端，最好放在data目录下，如
adb push c:\wherever_you_put\tcpdump /data/local/tcpdump
3.更改tcpdump文件的权限
adb shell chmod 777 /data/local/tcpdump
4.启动你要抓包的app，执行如下命令就可以开始抓包了，抓包文件以.pcap为后缀
adb shell tcpdump -p -vv -s 0 -w /sdcard/capture.pcap
# "-p": disable promiscuous mode (doesn't work anyway)
# "-s 0": capture the entire packet
# "-w": write packets to a file (rather than printing to stdout)
5.停止抓包，使用ctrl+C
... do whatever you want to capture, then ^C to stop it ...
6.导出转包文件
adb pull /sdcard/capture.pcap .
7.使用Wireshark将日志文件打开
