Unable to have a successful test with the "Connecting Nodes over an External Network" example

[TSC21]

Hi all,

First of all thanks for the great work done with this package and with the documentation provided!

Unfortunately though, following https://docs.vulcanexus.org/en/humble/rst/tutorials/core/deployment/external_locators/external_locators.html, I am unable to get the same results as the ones shown on the example there.

I have two laptops, where one would be host 1 and the other the host 2 as per the setup on the example as well. They can see each other, and I can ping both laptops from inside of each container in each laptop. Though, I cannot get the host 2 container 1 to listen to the talker on host 1 container 1. Even if I run the listener directly on host 2, I cannot listed to the talker on host 1 container 1. If I run the listener in host 1 container 2 or the host 1 itself it can listen to the talker on host 1 container 1. if I start the talker on the host 1 (outside of the container), and I start the listener on host 2 (outside of the container), the listener on host 2 can listen to the talker on host 1, so the LAN network is well setup and the two hosts can "see" each other.

The IP address on the host 1 in the WiFi LAN is 192.168.1.248 and this is its Profiles.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<dds>
    <profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles">
        <participant profile_name="container0" is_default_profile="true">
            <rtps>
                <!-- External locators for user traffic -->
                <default_external_unicast_locators>
                    <udpv4 externality="1" cost="0" mask="24">
                        <!-- Host 1 external IP -->
                        <address>192.168.1.248</address>
                        <port>11201</port>
                    </udpv4>
                </default_external_unicast_locators>
                <builtin>
                    <!-- External locators for discovery traffic -->
                    <metatraffic_external_unicast_locators>
                        <udpv4 externality="1" cost="0" mask="24">
                            <!-- Host 1 external IP -->
                            <address>192.168.1.248</address>
                            <port>11200</port>
                        </udpv4>
                    </metatraffic_external_unicast_locators>
                    <!-- Locators of remote participants (discovery traffic)-->
                    <initialPeersList>
                        <!-- Container 2 peer-->
                        <locator>
                            <udpv4>
                                <!-- Host 2 external IP -->
                                <address>192.168.1.234</address>
                                <port>11200</port>
                            </udpv4>
                        </locator>
                        <!--
                            Local network DDS default multicast to discover
                            other participants in the same LAN,
                            using External Locators, or not
                        -->
                        <locator>
                            <udpv4>
                                <address>239.255.0.1</address>
                                <port>7400</port>
                            </udpv4>
                        </locator>
                    </initialPeersList>
                </builtin>
            </rtps>
        </participant>
    </profiles>
</dds>

The IP address of host 2 in the WiFi LAN is 192.168.1.234, and this is its Profiles.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<dds>
    <profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles">
        <participant profile_name="container0" is_default_profile="true">
            <rtps>
                <!-- External locators for user traffic -->
                <default_external_unicast_locators>
                    <udpv4 externality="1" cost="0" mask="24">
                        <!-- Host 1 external IP -->
                        <address>192.168.1.234</address>
                        <port>11201</port>
                    </udpv4>
                </default_external_unicast_locators>
                <builtin>
                    <!-- External locators for discovery traffic -->
                    <metatraffic_external_unicast_locators>
                        <udpv4 externality="1" cost="0" mask="24">
                            <!-- Host 1 external IP -->
                            <address>192.168.1.234</address>
                            <port>11200</port>
                        </udpv4>
                    </metatraffic_external_unicast_locators>
                    <!-- Locators of remote participants (discovery traffic)-->
                    <initialPeersList>
                        <!-- Container 2 peer-->
                        <locator>
                            <udpv4>
                                <!-- Host 2 external IP -->
                                <address>192.168.1.248</address>
                                <port>11200</port>
                            </udpv4>
                        </locator>
                        <!--
                            Local network DDS default multicast to discover
                            other participants in the same LAN,
                            using External Locators, or not
                        -->
                        <locator>
                            <udpv4>
                                <address>239.255.0.1</address>
                                <port>7400</port>
                            </udpv4>
                        </locator>
                    </initialPeersList>
                </builtin>
            </rtps>
        </participant>
    </profiles>
</dds>

Another note is that I have Vulcanexus also installed on both hosts, where one host is running Ubuntu 20.04 with Galactic and the other Ubuntu 22.04 with Humble. And I have, in both, this in .bashrc:

source /opt/ros/<ros_version>/setup.bash
source /opt/vulcanexus/<ros_version>/setup.bash

where <ros_version> is the name of the release. The above source /opt/ros/<ros_version>/setup.bash is probably redundant, but I kept it anyway. I don't think the fact that I have it installed on both machines makes any difference considering I am trying to use the containers.

Any pointers on why I cannot successfully get the nodes to talk to each other? I assume it's something that might be missing or misconfigured on the profile configuration, but I am not sure.

@rsanchez15 @Mario-DL tagging you for visibility.

Thanks in advance for your help!

[Mario-DL]

Hi @TSC21,

Thanks for the detailed report. I had a look at the configuration file and it looks nice to me.

The problem seems to be that the minimum internal participant ID changed from 1 to 0 between galactic and humble, affecting the discovery.

Please, try it again launching the humble vulcanexus docker with the port mapping 11200-11201:7410-7411/udp instead. If that solves the issue, I will update it in the tutorial.

[TSC21]

@Mario-DL yes that seems to make it work. Thanks for the quick response!

[EduPonz]

For completion, this was changed in eProsima/Fast-DDS#3437, which was first made available in Fast DDS v2.11.0.