说明：  VB检测网络可到达性并测试网络连接速度，不是太准确，源代码是早几年的，有些地方有待完善，测试截图如上示。程序可以指定多个目标，点击“运行”后先检测是否可到达，然后检测连接速度，并显示出来，程序运行较慢，需等待。
(VB detect network reachability and test the network connection speed, not too accurate, the source code is a few years ago, some places need to be improved, test shots above show. Program can specify multiple targets, click on " Run" after the first test for accessible, and then test connection speed, and displayed, the program runs slower, need to wait.)