Building a Robot: ROS2 Pub-Sub

Sample to demonstrate how to create a ros2 Publisher and Subscriber. The sample is derived from ROS2 examples available here: ROS Tutorials

Assumptions

• Tested on ROS2 foxy or Galactic build.
• Tested on a Linux (Ubuntu ARM64 20.04.03) build so may not work on Windows or MacOS
• Both Publisher and Listener are communicating over demo_topic, this can be changed or parameterized in the packages.

Build Instructions

Use colcon to build and then source using the setup.bash in Install folder created in your ROS2 workspace.

# ensure any dependencies are managed before you build
rosdep install -i --from-path src --rosdistro galactic -y 
# build the packages 
colon build
# source install the packages into ros2
. install/setup.bash

Running the Sample in a ROS2 environment

Use the following commands from the root of your ROS2 workspace NOTE: Make sure you have sourced ros2 in the terminal, else all commands will fail:

source ~/<your ros2 installation>/setup.bash

In a new terminal start the Publisher:

[ROS2 Workspace Root]>> ros2 run demo_pub demo_pub_node

# Expected Output
[INFO] [1641630963.715973530] [demo_publisher]: Publishing: Hello World: 0
[INFO] [1641630964.203379204] [demo_publisher]: Publishing: Hello World: 1
[INFO] [1641630964.706833762] [demo_publisher]: Publishing: Hello World: 2

In another terminal start the Subscriber:

[ROS2 Workspace Root]>> ros2 run demo_sub demo_sub_node

# Expected Output
[INFO] [1641631802.220679292] [demo_subscriber]: Message received Hello World: 0
[INFO] [1641631802.707940321] [demo_subscriber]: Message received Hello World: 1
[INFO] [1641631803.213551280] [demo_subscriber]: Message received Hello World: 2