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Hi, I am working with ros2-dashing and I notice that when I don't check "unreliable" in rviz for a topic, rviz don't receive messages or raise the Could not transform from [odom] to [base_footprint] error. If I check unreliable (which made rviz subscribe udp ) the messages are received normally.

I don't understand the error, because I using a simulate robot in gazebo, and I can't see why network parameters could affect local simulations. This happens with the odom topic (error transform from base_footprint to odom ), which is generated by the gazebo diff drive plugin and with the lasers topics (0 messages receive ) which are generated by libgazebo_ros_ray_sensor plugin.

Does anyone face the same problem or have ideas what can be the source ?


Originally posted by jGany on ROS Answers with karma: 5 on 2020-06-18

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Comment by gvdhoorn on 2020-06-18:
I don't know for sure, but I could imagine reliable is mapped onto DDS QoS parameters with the same name (and otherwise it will be best effort for instance). DDS publishers/subscribers with different QoS settings can't always connect, which could be the cause of what you report.

See About Quality of Service settings - QoS compatibilities on the ROS Index for some more information.

I can't see why network parameters could affect local simulations

this doesn't have anything to do with which network you are using or not (well, not directly anyway). If it is the QoS settings, it will happen even if no networking is used at all.

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There are pairings of QoS settings in DDS (and by extension ROS2) that are incompatible with each other, you've found one such pair - that's why it doesn't work.

There are some tables on this page https://index.ros.org/doc/ros2/Concepts/About-Quality-of-Service-Settings/#qos-compatibilities which can help you understand those that are incompatible.


Originally posted by stevemacenski with karma: 8272 on 2020-06-18

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