Using Husarnet & ROS 2

ROS 2 and DDS Implementation

Both ROS and ROS 2 allow you to run nodes on different physical machines and they discover each other as long as they are in the same LAN network (with multicasting enabled). Therefore to run ROS on robotic systems distributed among multiple networks VPN is needed.

Husarnet is a peer-to-peer, low-latency and lightweight VPN dedicated for robotics applications. In this short guide we will show you how to configure ROS 2 to make it work with the Husarnet VPN client.

info

Basically "configure ROS 2" means "configure DDS" that is an abstraction layer ROS 2 is based on. DDS in scope of ROS 2 is often called a ROS Middleware Implementation and you can set it with RMW_IMPLEMENTATION environment variable. To use Husarnet with DDS some preconfiguration is needed. The specific configuration depends on which DDS implementation is used, but generally peers from Husarnet should be added to an XML configuration file.

There are various distributions of ROS 2, each with different default DDS installed:

Realase Date	ROS 2 Distro name	Default RMW implementation
2022	Humble (LTS)	Fast DDS
2021	Galactic	Cyclone DDS
2020	Foxy (LTS)	Fast DDS
2019	Dashing	Fast DDS

In the next sections we will present how to configure two most popular DDS implementations on a system running ROS 2: Cyclone DDS and eProsima Fast DDS. They both just work with Husarnet so the choice is yours.

Let's start with creating a VPN network for your devices...

Install Husarnet VPN client

Execute this command on each physical device you need to connect.

curl -s https://install.husarnet.com/install.sh | sudo bash

Create Husarnet network

Add your physical devices to the same Husarnet network, by executing following commands on each of them:

husarnet join <your-join-code> <device-hostname>

More information at: Getting Started Guide for Linux

Using Fast DDS

Install

If the default DDS implementation used in you ROS 2 distribution is different than FastDDS, you need to install it:

sudo apt-get update
sudo apt-get install ros-$ROS_DISTRO-rmw-fastrtps-cpp
export RMW_IMPLEMENTATION=rmw_fastrtps_cpp

Configure

Create a Fast DDS configuration file in your ROS 2 workspace: ~/fastdds_husarnet.xml

To make the communication work, you have to set some parameters as shown in the following template.

IMPORTANT: Provide all peers under initialPeersList tag.

<?xml version="1.0" encoding="UTF-8" ?>
<profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles">
    <transport_descriptors>
        <transport_descriptor>
            <transport_id>HusarnetTransport</transport_id>
            <type>UDPv6</type>
        </transport_descriptor>
    </transport_descriptors>

    <participant profile_name="CustomHusarnetParticipant" is_default_profile="true">
        <rtps>
            <userTransports>
                <transport_id>HusarnetTransport</transport_id>
            </userTransports>
            <useBuiltinTransports>true</useBuiltinTransports>
            <builtin>
                <initialPeersList>
                <!-- Repeat this part for each husernet peer -->
                    <locator>
                        <udpv6>
                            <address>husarnet-IPv6-address</address> <!-- or <address>husarnet-hostname</address> -->
                        </udpv6>
                    </locator>
                <!-- End repeat -->
                </initialPeersList>
            </builtin>
        </rtps>
    </participant>
</profiles>

Launch the configuration

Set this file as default profile in your .bashrc file, so as to use this configuration every time you boot your system. Open a new terminal and execute:

echo "export RMW_IMPLEMENTATION=rmw_fastrtps_cpp" >> ~/.bashrc
echo "export FASTRTPS_DEFAULT_PROFILES_FILE=/home/$USER/fastdds_husarnet.xml" >> ~/.bashrc
. ~/.bashrc

Test

Now you will be able to use your default ROS 2 tools with Husarnet:

Run a publisher and subscriber demo, from demo-nodes-cpp package. To install it run:

sudo apt-get update
sudo apt-get install -y ros-$ROS_DISTRO-demo-nodes-cpp

At the first physical machine execute in the terminal:

ros2 run demo_nodes_cpp talker

And this command at the second:

ros2 topic echo /chatter

You should receive messages from talker on your second, Husarnet connected host.

Using Cyclone DDS

Install

If the default DDS implementation used in you ROS 2 distribution is different than Cyclone, you need to install it:

sudo apt-get update
sudo apt-get install ros-$ROS_DISTRO-rmw-cyclonedds-cpp
export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp

Configure

Create communication settings file, for example in your home directory /home/$USER/cyclonedds.xml

To make communication work you have to set some params as follows:

<?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>
            <NetworkInterfaceAddress>hnet0</NetworkInterfaceAddress>
            <AllowMulticast>false</AllowMulticast>
            <MaxMessageSize>65500B</MaxMessageSize>
            <FragmentSize>4000B</FragmentSize>
            <Transport>udp6</Transport>
        </General>      
        <Discovery>
            <Peers>
                <Peer address="[IPV6-address]"/> <!-- example: <Peer address="[fc94:dd2c:a2e6:d645:1a36:****:****:****]"/> -->
                <Peer address="[hostname]"/> <!-- example: <Peer address="[my-laptop]"/> -->
            </Peers>
            <ParticipantIndex>auto</ParticipantIndex>
        </Discovery>
        <Internal>
            <Watermarks>
                <WhcHigh>500kB</WhcHigh>
            </Watermarks>
        </Internal>
        <Tracing>
            <Verbosity>severe</Verbosity>
            <OutputFile>stdout</OutputFile>
        </Tracing>
    </Domain>
</CycloneDDS>

You can provide Peer as IPv6 address or hostname from Husarnet.

IMPORTANT: Provide all peers <hostnames/IPv6 address>, (chose one) in every machine.

Important fields:

1. NetworkInterfaceAddress <NetworkInterfaceAddress>hnet0</NetworkInterfaceAddress> - force DDS to use hnet0 network interface (the one created in your host OS by Husarnet VPN).

2. Multicast <AllowMulticast>false</AllowMulticast>. At the time of writing this file multicast is not supported by Husarnet so it's necessary to disable this. Multicast feature will be added soon.

3. Transport Protocol <Transport>udp6</Transport>. It's necessary to use IPv6 but Cyclone doesn't allow to mix IPv4 with IPv6 so every node must communicate over IPv6.

4. IPV6-address <Peers><Peer address="[IPV6-address]"/></Peers>. Here appropriate IP addresses should be filled, you can take this address form Husarnet WebUI. Safe method is to provide address of local IPv6 and remote machines.

If you need information about params check cyclonedds-manual

Launch the configuration

Add changes to .bashrc file to use that configuration every time you boot your system. Open a new terminal and execute:

echo "export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp" >> ~/.bashrc
echo "export CYCLONEDDS_URI=file:///home/$USER/cyclonedds.xml" >> ~/.bashrc
. ~/.bashrc

Test

Run a publisher and subscriber demo, from demo-nodes-cpp package. To install it run:

sudo apt-get update
sudo apt-get install -y ros-$ROS_DISTRO-demo-nodes-cpp

At the first physical machine execute in the terminal:

ros2 run demo_nodes_cpp talker

And this command at the second:

ros2 topic echo /chatter

Summary

As you can see using Husarnet with ROS 2 and Cyclone DDS or Fast DDS is very easy.

In case of any questions related to this article please contact us using Husarnet Community Forum or via email at support@husarnet.com.

tip

Husarnet ROS 2 Docker base images

If you are a Docker user, then using Husarnet with your ROS 2 docker images might be even easier, because the DDS setup will be done automatically.

Visit https://github.com/husarnet/ros to learn more.

Read also ...

• Connecting Remote Robots Using ROS 2, Docker & VPN
• Scalable Distributed Robot Fleet With Fast DDS Discovery Server