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ROS2: can see topic but no data

asked 2020-07-29 12:53:36 -0500

naaju gravatar image

Hi there,

I have a question about running ROS2 on severtal machines.I have 4 machines, all Ubuntu 18.04. Two of them are VMs in the cloud and two are local machines. All four machines are connected via VPN.

First I tried the talker listener example. All machines got the data on the /chatter topic, so far so good.

I have now connected an IntelRealsense D415 camera to the local machine. I can also visualize the images in rviz on the local machine. If I now enter ros2 topic list on a machine in the cloud, I can see all topics. But when I enter ros2 topic echo /camera/color/image_raw, no data is received. Additionally it is strange that I receive data under ros2 topic echo /camera/color/camera_info

Does anyone know why this is happening?

regards Julian

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answered 2020-07-30 01:31:10 -0500

ahcorde gravatar image


If you are publising a big amount of data you should take a look to this tutorial. You will probably need to modify your network configuration.

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another problem could be the visibility between your machines. Edit your /etc/hosts file to include all the IPs

ahcorde gravatar image ahcorde  ( 2020-07-30 01:32:30 -0500 )edit

Hello, but if it is because of visibility, I could not see the topics, or am I wrong?

naaju gravatar image naaju  ( 2020-07-30 02:43:02 -0500 )edit

I think I fall in this error some time ago using Docker containers. Just give it a try and let me know if it works for you ;)

ahcorde gravatar image ahcorde  ( 2020-07-30 08:19:44 -0500 )edit

Hey, so I increased the ipfrag_high_thresh parameter and the communication between the local machines works now. But the data is not available in the cloud. I wonder if it could possibly be a problem with the package sizes.

naaju gravatar image naaju  ( 2020-07-30 09:11:30 -0500 )edit

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Asked: 2020-07-29 12:53:36 -0500

Seen: 160 times

Last updated: Jul 30 '20