Summary

With this chapter, you have discovered the most important ROS 2 concepts: nodes, topics, services, actions, parameters, and launch files.

ROS 2 programs are called nodes. Simply put, they are regular software programs that can also benefit from ROS 2 functionalities: logs, communications, parameters, and so on.

There are three types of communication: topics, services, and actions. Topics are used to send a stream of data/commands from one or several nodes to another or several other nodes. Services are used when we need client/server communication. Actions are basically the same things as services, but for goal executions that could take some time.

On top of communication features, nodes can also use parameters to specify settings at runtime. Parameters allow nodes to be easily configured when started.

Finally, we can start all nodes and parameters from just one command line, using a launch file.

That’s it for the core concepts (for now). You have also...