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CycloneDDS unicast between machine

Disable multicast discovery and allow unicast traffic between two machines

Demo

graph TD
    subgraph MachineA [Machine A]
        A1[eth0: 192.168.1.10]
        A2[eth1: 10.0.0.1]
    end

    subgraph MachineB [Machine B]
        B1[eth0: 10.0.0.4]
    end

    A2 --- B1
Sender
cyclondedds.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>false</AllowMulticast>

    </General>
    <Discovery>
      <ParticipantIndex>auto</ParticipantIndex>
      <Peers>
        <Peer Address="10.0.0.4" />
        <Peer Address="127.0.0.1" />
      </Peers>
    </Discovery>
  </Domain>
</CycloneDDS>
Receiver
cyclondedds.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>false</AllowMulticast>
    </General>
    <Discovery>
    <ParticipantIndex>auto</ParticipantIndex>
      <Peers>
        <Peer Address="10.0.0.1" />
        <Peer Address="127.0.0.1" />
      </Peers>
    </Discovery>
  </Domain>
</CycloneDDS>

peer localhost

<Peer Address="127.0.0.1" />

This is essential because Cyclone DDS does not automatically assume loopback (127.0.0.1) unless you’re using multicast or explicitly list it.

env.sh
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export CYCLONEDDS_URI=file://$PWD/cyclonedds.xml
source /opt/ros/humble/setup.bash
export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp

usage

We can run the pub/sub on both side

pub
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source env.sh
ros2 topic pub xxx std_msgs/String "data: hello world" -r 1
echo
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source env.sh
ros2 topic echo /xxx

ros2 daemon

The ROS2 daemon is a background process that:

  • Caches discovered ROS nodes and topics
  • Improves discovery performance
  • Manages node name resolution

Some time we need to restart for refresh discovery when using ROS commands

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ros2 daemon stop && ros2 daemon start