网络不通的时候，用ping的方式，测试网络是否畅通。可以将窗体最小化，待网络畅通后，可以自动弹出窗体提醒。可设置ping命令间隔-No Network when using ping at testing the network is open. Forms can be minimized until the network flow, you can automatically pop up to remind the form. Interval can be set to the ping command