Writing an action client
We now have the minimal code required for the server to receive a goal, accept it, execute it, and return a result. At this point, we can write the client side of the communication.
The action client will send a goal to the server. It will then register a callback to find out whether the goal was accepted or rejected. If the goal is accepted, the client will register yet another callback to get the final result. That’s what we’re going to implement now—first with Python, then with C++.
Where should you write the action client? In your own ROS 2 applications, you could add an action client to any node. As an example, let’s say you have a node that monitors the battery level of a mobile robot. This node could already have some publishers, subscribers, services, and so on. On top of all that, you can add an action client that will send a goal to another node (such as the server node, which controls the wheels of the robot) when...
