At the beginning of the Unit 4 we are asked to list the available services and use two of them. However they are not present.
For example command ros2 service list | grep moving does not print anything and ros2 service call /moving std_srvs/srv/Empty prints out waiting for service to become available....
Since I created the thread, I have another small piece of feedback. There is a typo towards the end of Example 4.2. Before the command ros2 service call /stop std_srvs/srv/Empty, there is a paragraph saying: Do you remember there was another Service called /stopped? Try to use it. But the service is named /stop, not /stopped. Other references to this service in the text seem to be correct.