This package provides a network bridge which enables to exchange messages between ROS 1 and ROS 2.
The bridge is currently implemented in C++ simply because there is no Python API for ROS 2 yet. Therefore it is limited to all the message types available at compile time.
In order to run the bridge you need to either:
- get prebuilt binaries or
- build the bridge as well as the other ROS 2 packages from source.
After that you can run both examples described below.
For all examples you need to source the environment of the ament install space where the bridge was built in or unpacked to.
Additionally you will need to either source the ROS 1 environment or at least set the ROS_MASTER_URI and run a roscore.
The following ROS 1 packages are required to build and use the bridge:
catkinroscpprosmsgstd_msgs- as well as the Python package
rospkg
Before continuing you should have ROS 2 built from source following these instructions.
Note: you need almost 4 GB of free RAM per thread to compile the bridge.
This will be fixed once rclcpp has been refactored into a library.
The bridge uses pkg-config to find ROS 1 packages.
ROS 2 packages are located in CMake using find_package().
Therefore the CMAKE_PREFIX_PATH must not contain paths from ROS 1 which would overlay ROS 2 packages.
In order to build this ament package you must first setup the ROS 1 environment:
. /opt/ros/indigo/setup.bash
unset CMAKE_PREFIX_PATH
and second source the ROS 2 environment:
. <workspace-with-ros2>/install/setup.bash
Afterwards you can build the ament package as usual. Due to the high memory usage you might want to restrict the number of parallel jobs.
Note: due to a bug in ROS 1 rosbag you currently must patch an installed file or build ROS 1 ros_comm from source.
Edit the file /opt/ros/indigo/lib/python2.7/dist-packages/rosbag/bag.py with root permissions and comment out the line containing import roslz4.
Make sure to revert the change after building the bridge.
The next ROS 1 patch release will resolve this problem (ros/ros_comm#642).
ament build <workspace-with-bridge> --make-args -j1
The talker and listener can be either a ROS 1 or a ROS 2 node. The bridge will pass the message along transparently.
First we start a ROS 1 roscore:
# Shell A:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
roscore
Then we start the dynamic bridge which will watch the available ROS 1 and ROS 2 topics. Once a matching topic has been detected it starts to bridge the messages on this topic.
# Shell B:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
. <install-space-with-bridge>/setup.bash
export ROS_MASTER_URI=http://localhost:11311
dynamic_bridge
The program will start outputting the currently available topics in ROS 1 and ROS 2 in a regular interval.
Now we start the ROS 1 talker.
# Shell C:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
rosrun rospy_tutorials talker
The ROS 1 node will start printing the published messages to the console.
Now we start the ROS 2 listener.
# Shell D:
. <install-space-with-ros2>/setup.bash
listener
The ROS 2 node will start printing the received messages to the console.
When looking at the output in shell B there will be a line stating that the bridge for this topic has been created:
created 1to2 bridge for topic 'chatter' with ROS 1 type 'std_msgs/String' and ROS 2 type 'std_msgs/String'
At the end stop all programs with Ctrl-C.
Once you stop either the talker or the listener in shell B a line will be stating that the bridge has been teared down:
removed 1to2 bridge for topic 'chatter'
The screenshot shows all the shell windows and their expected content:
The steps are very similar to the previous example and therefore only the commands are described.
# Shell A:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
roscore
# Shell B:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
. <install-space-with-bridge>/setup.bash
export ROS_MASTER_URI=http://localhost:11311
dynamic_bridge
Now we start the ROS 2 talker.
# Shell C:
. <install-space-with-ros2>/setup.bash
talker
Now we start the ROS 1 listener.
# Shell D:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
rosrun roscpp_tutorials listener
The second example will demonstrate the bridge passing along bigger and more complicated messages.
A ROS 2 node is publishing images retrieved from a camera and on the ROS 1 side we use rqt_image_view to render the images in a GUI.
And a ROS 1 publisher can send a message to toggle an option in the ROS 2 node.
First we start a ROS 1 roscore and the bridge:
# Shell A:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
roscore
# Shell B:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
. <workspace-with-bridge>/install/setup.bash
export ROS_MASTER_URI=http://localhost:11311
dynamic_bridge
Now we start the ROS 1 GUI:
# Shell C:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
rqt_image_view
Note: The currently released version of rqt_image_view does not allow to specify the topic name on the command line.
And since the GUI only shows available ROS 1 topics and for resource reasons the bridge only starts bridging messages once publishers and subscribers are available on both sides the ROS 2 topic won't be listed.
Therefore we have to briefly start a ROS 1 publisher to workaround the limitation of rqt_image_view.
# Shell D:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
rosrun usb_cam usb_cam_node usb_cam/image_raw:=image
While the usb_cam_node process is running you should be able to select the /image topic in rqt_image_view and see the current images.
Now we can stop the usb_cam_node process in shell D with Ctrl+C
--
Now we start the ROS 2 image publisher:
# Shell E:
. <workspace-with-ros2>/install/setup.bash
cam2image
You should see the current images in rqt_image_view which are coming from the ROS 2 node cam2image and are being passed along by the bridge.
--
To exercide the bridge in the opposite direction at the same time you can publish.
You can either use the Message Publisher plugin in rqt to publish a std_msgs/Bool message on the topic flip_image.
By publishing either true or false the camera node with conditionally flip the image before sending it.
As an alternative you can also run one of the two following rostopic commands:
# Shell F:
. /opt/ros/indigo/setup.bash
# Or, on OSX, something like:
# . ~/ros_catkin_ws/install_isolated/setup.bash
rostopic pub -r 1 /flip_image std_msgs/Bool "{data: true}"
rostopic pub -r 1 /flip_image std_msgs/Bool "{data: false}"
The screenshot shows all the shell windows and their expected content:
