画流程图的好例子，作者自己封装了一个类，可以自己扩展功能，也可以加以修改用来画网络拓扑图-painting flowchart good example of the author himself Packaging, a category of their own expansion, modifications can be used to draw network topology, etc.

一个通信节点拓扑图,可动态添加,删除节点,连线等.