可以ping至多4个url，并且告诉用户那些url是可以访问的，同时提供rrt时间供用户参考-You can ping up to four url, url and tell the user that is accessible, while providing time for user reference rrt

RRT is a widely used method of robot path planning, path planning are processed in a different problem-RRT is a widely used method of robot path planning, path planning are processed in a different problem,,

在ros平台下实现rrt算法，可以使用rviz仿真，方便算法开发。(In the ROS platform to achieve RRT algorithm, you can use rviz simulation, easy to develop algorithms.)