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Holoscan ROS2 Publisher/Subscriber Examples#

Authors: Holoscan SDK Team (NVIDIA)
Supported platforms: x86_64, aarch64
Language: C++
Last modified: September 2, 2025
Latest version: 1.0.0
Minimum Holoscan SDK version: 3.0
Tested Holoscan SDK versions: 3.0
Contribution metric: Level 1 - Highly Reliable

Overview#

This application demonstrates basic communication between Holoscan and ROS2, containing both publisher and subscriber examples in a single combined structure. The examples show how to: - Send simple string messages from Holoscan to ROS2 (Publisher) - Receive messages from ROS2 in Holoscan operators (Subscriber) - Bridge data between the two frameworks

Both C++ and Python implementations are included, with the publisher and subscriber components organized under shared cpp/ and python/ directories.

File Structure#

applications/holoscan_ros2/pubsub/
├── CMakeLists.txt          # Top-level build configuration
├── README.md               # This file
├── cpp/                    # C++ implementations
│   ├── CMakeLists.txt      # C++ build configuration
│   ├── metadata.json       # C++ application metadata
│   ├── talker.cpp          # Publisher implementation
│   └── listener.cpp        # Subscriber implementation
└── python/                 # Python implementations
    ├── CMakeLists.txt      # Python build configuration
    ├── metadata.json       # Python application metadata
    ├── talker.py           # Publisher implementation
    └── listener.py         # Subscriber implementation

Note: This structure combines the previously separate holoscan_ros2_simple_publisher and holoscan_ros2_simple_subscriber applications into a single, more organized layout. All functionality remains the same, but both components are now built and managed together.

Prerequisites#

  • NVIDIA Holoscan SDK v3.0 or later
  • ROS2 Jazzy (all examples and Dockerfiles are tested with Jazzy; other distributions may work but are not tested)
  • Docker (with NVIDIA Container Toolkit and a recent version)
  • NVIDIA GPU drivers (suitable for your hardware and Holoscan SDK)

Building the Application#

Build the combined publisher/subscriber application: 

./holohub build pubsub

This single command builds both the publisher and subscriber components for both C++ and Python.

Application Modes#

The pubsub application uses modes to handle the publisher and subscriber components. You can list available modes using: 

./holohub modes pubsub --language cpp
./holohub modes pubsub --language python

Available modes: - publisher: Sends simple string messages to ROS2 topic (default mode) - subscriber: Receives messages from ROS2 topic

Running C++ Publisher and Subscriber#

Run the Publisher and the Subscriber components in different consoles. Use the modes feature to specify which component to run.

Publisher component: 

./holohub run pubsub publisher --language cpp
# Or simply (since publisher is the default mode):
./holohub run pubsub --language cpp

Expected output: 

Publishing: 'Hello, world! 12'
Publishing: 'Hello, world! 13'
Publishing: 'Hello, world! 14'
...

Subscriber component: 

./holohub run pubsub subscriber --language cpp

Expected output: 

I heard: 'Hello, world! 12'
I heard: 'Hello, world! 13'
I heard: 'Hello, world! 14'
...

Validation: - The publisher should output periodic "Publishing" logs with incrementing numbers - The subscriber should output corresponding "I heard" logs with matching messages - Messages should match between publisher and subscriber

Running Python Publisher and Subscriber#

Run the Publisher and the Subscriber components in different consoles. Use the same modes as the C++ version.

Publisher component: 

./holohub run pubsub publisher --language python
# Or simply (since publisher is the default mode):
./holohub run pubsub --language python

Subscriber component: 

./holohub run pubsub subscriber --language python

Validation: - Similar to C++ examples, you should see matching publish/receive logs - Python and C++ versions are interoperable (you can mix languages)

Additional Resources#

Documentation#

  • Applications Overview: ../ - Background on ROS2 and Holoscan integration
  • Camera Examples: ../vb1940/ - Advanced camera integration with VB1940 hardware
  • Bridge Library: ../../../operators/holoscan_ros2/ - Bridge implementation and headers

Community and Support#