Verify Jazzy With Talker and Listener

A successful package installation is useful evidence.

A communicating ROS system is stronger evidence.

The Jazzy Ubuntu installation guide ends with a simple test using packaged demo nodes.

Terminal A: talker

Open a terminal and source Jazzy:

source /opt/ros/jazzy/setup.bash
ros2 run demo_nodes_cpp talker

You should see the talker publishing messages.

Leave it running.

Terminal B: listener

Open a second terminal and source Jazzy again:

source /opt/ros/jazzy/setup.bash
ros2 run demo_nodes_py listener

You should see the listener report that it heard the messages.

What this proves

This small experiment exercises more than one command:

ROS packages discoverable
        ↓
C++ demo executable starts
        ↓
publisher node participates in graph
        ↓
Python demo executable starts
        ↓
subscriber node participates in graph
        ↓
messages move between them

You do not need to understand the middleware internals yet.

At this point, the useful beginner claim is simply:

Two ROS 2 nodes discovered each other and exchanged typed messages.

Inspect while they run

In a third sourced terminal, run:

ros2 node list
ros2 topic list

Do not worry about every name yet. Just prove the running system is visible to ROS 2 introspection tools.

Stop cleanly

Use Ctrl+C in the talker and listener terminals.

Evidence checkpoint

Save:

• one talker output sample;
• one matching listener output sample;
• the node list while both were running;
• a one-paragraph explanation of what the test proves and what it does not prove.