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

Note: By default, the demo executables will spin up the SingleThreaded executor if run in separate processes, i.e., not composed in the same component container. To configure the demo executables to run with a different executor, build the package with the custom DEMO_EXECUTOR flag set to the fully qualified name of the executor. For example, to run with the experimental EventsExecutor,

colcon build --packages-select demo_nodes_cpp --cmake-args -DDEMO_EXECUTOR:STRING=rclcpp::experimental::executors::EventsExecutor

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

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Changelog for package demo_nodes_cpp

0.33.5 (2024-09-06)

0.33.4 (2024-06-27)

0.33.3 (2024-05-13)

• [demo_nodes_cpp] some readme and executable name fixups (#678) (#688) (cherry picked from commit aa8df8904b864d063e31fd5b953ffe561c7a9fe0) Co-authored-by: Mikael Arguedas <<mikael.arguedas@gmail.com>>

• Fix gcc warnings when building with optimizations. (#672) (#673)

  * Fix gcc warnings when building with optimizations. When building the allocator_tutorial_pmr demo with -O2, gcc is throwing an error saying that new and delete are mismatched. This is something of a misnomer, however; the real problem is that the global new override we have in that demo is actually implemented incorrectly. In particular, the documentation at https://en.cppreference.com/w/cpp/memory/new/operator_new very clearly specifies that operator new either has to return a valid pointer, or throw an exception on error. Our version wasn't throwing the exception, so change it to throw std::bad_alloc if std::malloc fails. While we are in here, also fix another small possible is where std::malloc could return nullptr on a zero-sized object, thus throwing an exception it shouldn't.

  * Always inline the new and delete operators. That's because gcc 13 has a bug where it can sometimes inline one or the other, and then it detects that they mismatch. For gcc and clang, just force them to always be inline in this demo.

  * Switch to NOINLINE instead. Both clang and MSVC don't like inlining these, so instead ensure that they are not inlined. This also works because the problem is when new is inlined but not delete (or vice-versa). As long as they are both not inlined, this should fix the warning. (cherry picked from commit 957ddbb9f04f55cabd8496e8d74eb35ee4d29105) Co-authored-by: Chris Lalancette <<clalancette@gmail.com>>

• Contributors: mergify[bot]

0.33.2 (2024-03-28)

• A few uncrustify fixes for 0.78. (#667)
• Allow users to configure the executor for executables in [demo_nodes_cpp]{.title-ref} (#666)
• Update maintainer list in package.xml files (#665)
• Contributors: Chris Lalancette, Michael Jeronimo, Yadu

0.33.1 (2024-02-07)

0.33.0 (2024-01-24)

0.32.1 (2023-12-26)

• Added extra documentation and clarifications. (#651)
• Contributors: jrutgeer

0.32.0 (2023-11-06)

• Add in support for both the PMR and custom allocator tutorials. (#655)
• Replacing old-style C++ allocator with a polymorphic memory resource (PMR) (#653)
• Contributors: Ali Ashkani Nia, Chris Lalancette

0.31.1 (2023-09-07)

• Remove unnecessary captures in the various demos. (#647)
• Contributors: Chris Lalancette

0.31.0 (2023-08-21)

• Dramatically speed up the demo_nodes_cpp tests (#641)
• Switch to using RCLCPP logging macros in the lifecycle package. (#644)
• Contributors: Chris Lalancette

0.30.1 (2023-07-11)

• failed to call introspection_client (#643)
• Contributors: Chen Lihui

0.30.0 (2023-06-12)

• Small cleanups to the demos when running through them. (#639)

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