Hello!
I can use joystick to make the cf "takeoff" and "land" successfully after roslaunch "hover_swarm.launch" and "mocap_helper.launch". But when i run the "hello_world.py", it got stuck, just like the situation in disussions/328:

If hello_world.py does not terminate, try putting some print statements in between the lines to see how far it gets. Most likely, there is some problem in communication between the script and the Crazyswarm server, and it is getting stuck waiting for ROS services in the Crazyswarm() constructor. Make sure you source devel/setup.bash in the terminal from which you run hello_world.py.

However, if you see the Takeoff! printout from the Crazyswarm server when pressing the start button on the controller, but nothing happens, that suggests a problem in communication between the Crazyswarm server and the Crazyflies.

Originally posted by @jpreiss in #328 (comment)

Although i sourced "ros_ws/devel/setup.bash", the script still could not communicate with Crazyswarm server. I printed some sentences in 'Crazyswarm()', and founed it stucked here.
I searched for relevant issues in 'issues' and' discussions', but couldn't find a solution.

Your help is really appreciated, thanks in advance!