说明：  linux下多线程网络编程，实现arm9视频采集和网络发送jpeg数据，使用udp协议，自己写的，搞了好几天！linux下的多线程比较复杂易出错。
(linux network under the multi-threaded programming, video capture and realize ARM9 send jpeg data network, using udp protocol, wrote it myself, engaged in for several days! linux under the more complicated multi-threaded, error-prone.)