网络白板，采用c/s架构。用户可以画图，移动画图，共享画图的画面。聊天。运行时先运行net_write_server服务器。然后运行user_login来登陆用户进行网络白板-Network whiteboard, using c/s architecture. Users can draw, move the drawing, shared drawing screen. Chat. First run net_write_server server is running. Then run