简单实现原理：
      以太网使用lwip，netconn API编程，这种编程方式相比RAW 比较简单，只是需要OS的支持；然后，板子当服务器，PC当客户端，当建立连接后，服务器将采集到的摄像头数据发送到客户端显示
关键代码：

    系统(ucos_ii)中建立了两个任务，task1用来处理服务器的一些周期性任务，task2用来发送JPEG数据流。

/**
* @brief  TCP服务器任务
* @param  
* @retval None
*/
void TCP_Server_task(void *arg)
{
       err_t err=0;
       err_t recv_err;
       struct netconn *server_coon; //服务器连接

       struct netbuf *recvbuf;             //接收数据netbuf指针        
       struct pbuf *bufptr;         //pbuf数据缓冲区指针
       
       server_coon = netconn_new(NETCONN_TCP);                 //创建一个TCP链接
       netconn_bind(server_coon,IP_ADDR_ANY,TCP_SERVER_PORT);  //绑定端口 
       netconn_listen(server_coon);                            //进入监听模式
       server_coon->  recv_timeout = 10;                         //禁止阻塞线程 等待10ms
        
       while (1)   
       {
                 err = netconn_accept(server_coon,&client_conn);        //接收连接请求
                 //printf("\r\nerr=0x%x\r\n",err);
               if (err == ERR_OK)                                     //正确说明有客户端联入
                 {                                                 
                         while(1)
                               {                                
                                       if((recv_err = netconn_recv(client_conn,&recvbuf)) == ERR_OK)          //接收到数据且正确
                                       {                
                                               bufptr=recvbuf->  p;                                  //得到数据指针
                                               memcpy(Data_buff,bufptr->  payload,bufptr->  tot_len);  //拷贝数据                                       
                                               Data_buff[bufptr->  tot_len]='\0';                        //加入结束符
                                               
                                               if(!memcmp(Data_buff,Video_Start,9))               //开始采集
                                               {                     
                                                       Video_flag=1;                                   //标志位值1
                                                       CamFrame=0;                                   //帧率清零
                                                       cam_start();                                   //开始采集
                                                       RTC_ITConfig(RTC_IT_WUT,ENABLE);
                                               }
                                               else if(!memcmp(Data_buff,Video_Stop,8))            //关闭采集
                                               {         ......

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