What Is This?

This package provides several examples that demonstrate various inter-node communcations in ROS 2.

This package consists of the following examples:

1. add_two_ints_client
2. listener_serialized_message
3. reuse_timer
4. add_two_ints_client_async
5. list_parameters
6. set_and_get_parameters
7. add_two_ints_server
8. list_parameters_async
9. set_and_get_parameters_async
10. allocator_tutorial
11. one_off_timer
12. set_parameters_callback
13. content_filtering_publisher
14. parameter_blackboard
15. talker
16. content_filtering_subscriber
17. parameter_event_handler
18. talker_loaned_message
19. even_parameters_node
20. parameter_events
21. talker_serialized_message
22. listener
23. parameter_events_async
24. listener_best_effort
25. matched_event_detect

Build

Run the command below to compile the demo_nodes_cpp ROS 2 package:

colcon build --packages-up-to demo_nodes_cpp

Run

Basic Talker & Listener

This runs a basic ROS 2 publisher and subscriber that exchanges the following string message with an incrementing integer:

Hello World:

Talker

# Open new terminal
ros2 run demo_nodes_cpp talker

Listener [Default]

# Open new terminal
ros2 run demo_nodes_cpp listener

Listener [Best Effort]

Compared to Listener [Default], listener_best_effort runs a ROS 2 subscriber node that sets the Quality of Service (QoS) Reliability setting to Best Effort via the use of rclcpp::SensorDataQoS, as opposed to the default Reliable.

Messages sent using this policy configuration attempts to deliver samples but may lose them if the network is not robust.

# Open new terminal
ros2 run demo_nodes_cpp listener_best_effort

Basic Server & Client

This runs a ROS 2 server that provides a service to process two integers, outputting the sum back to ROS 2 client node.

Server

# Open new terminal
ros2 run demo_nodes_cpp add_two_ints_server

Client [Synchronous]

# Open new terminal
ros2 run demo_nodes_cpp add_two_ints_client

Client [Asynchronous]

# Open new terminal
ros2 run demo_nodes_cpp add_two_ints_client_async

File truncated at 100 lines see the full file