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CycloneDDS XML configuration

Default Multicast Behavior in CycloneDDS (ROS 2 Humble)

Settings Default Value
Discovery (SPDP) Multicast Enabled
User Data (Topic Data) Unicast Only
Meta Traffic (SEDP, other discovery traffic) Unicast Only

Demo

Send image data using gscam package and subscribe using rqt_image_viewer and ros2 topic echo measure/monitor the data using bmon tool

installation
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sudo apt install bmon
sudo apt install ros-humble-gscam
bmon
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bmon
terminal1
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export GSCAM_CONFIG="videotestsrc pattern=snow ! video/x-raw,width=640,height=480,framerate=30/1 ! videoconvert"
ros2 run gscam gscam_node

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ros2 run rqt_image_view rqt_image_view

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ros2 topic echo /camera/image_raw

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Multicast

For easy of use , using tmuxp yaml file to run all the test together

temp.xml
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<?xml version="1.0" encoding="UTF-8"?>
<CycloneDDS xmlns="https://cdds.io/config" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://cdds.io/config https://raw.githubusercontent.com/eclipse-cyclonedds/cyclonedds/master/etc/cyclonedds.xsd">
  <Domain Id="any">
    <General>
      <AllowMulticast>true</AllowMulticast>
    </General>
  </Domain>
</CycloneDDS>

tmuxp script

tmuxp_demo_multicast.yaml
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session_name: dds
windows:
  - window_name: cyclone
    layout: tiled
    suppress_history: false
    shell_command_before:
      - source /opt/ros/humble/setup.bash
    panes:
      - shell_command: #
          - export GSCAM_CONFIG="videotestsrc pattern=snow ! video/x-raw,width=640,height=480,framerate=30/1 ! videoconvert"
          - export CYCLONEDDS_URI=file://$PWD/temp.xml
          - ros2 run gscam gscam_node
      - shell_command: #
          - export CYCLONEDDS_URI=file://$PWD/temp.xml
          - ros2 run rqt_image_view rqt_image_view

      - shell_command:
          - export CYCLONEDDS_URI=file://$PWD/temp.xml
          -  # ros2 topic echo /camera/image_raw

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tmuxp load tmuxp_demo_multicast.yaml

multicast with one subscriber

lo

The communication use lo interface
by default lo not support multicast

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multicast with two or more subscriber

wlo1

The communication use the physical adapter (wlo1)
support multicast

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Reference