[ros-users] multi-machine communication problem

[Adam Leeper]

Hi-

I am trying to run a camera that is plugged into my laptop and I want to
publish messages that can be received by processes running on the robot
and/or basestation. I have correctly set the ROS_MASTER_URI to point to the
robot. I can tell because if I rostopic list on my laptop I get all the
robot topics, and if I run rviz I can also see all the robot state and
sensor data. For some reason though, it seems my laptop is not able to
publish messages back to the robot or basestation. The laptop is physically
connected to the same switch as the basestation and robot through an
ethernet cable.

>From my laptop I have a node publishing an image topic, called
/camera/image. On both the laptop and the basestation I have image_view
nodes subscribed to the /camera/image.

On my laptop the image_view window shows the image as expected. Doing
rostopic info /camera/image shows that there are two image_view processes
subscribed to the topic (one from the laptop and one from the basestation).

rostopic info /camera/image
Type: sensor_msgs/Image

Publishers:
 * /uvc_cam (http://jks-g51:59684/)

Subscribers:
 * /image_view_1279845826710500129 (http://jks-g51:33511/)
 * /image_view_1279846165570567012 (http://stair4-basestation:41138/)



On the basestation the image_view window does NOT show the image at all.
Doing rostopic hz/echo /camera/image shows no imcoming messages. However,
rostopic list still shows the /camera/image topic, and doing rostopic info
shows the same info as from the laptop.

rostopic info /camera/image
Type: sensor_msgs/Image

Publishers:
 * /uvc_cam (http://jks-g51:59684/)

Subscribers:
 * /image_view_1279845826710500129 (http://jks-g51:33511/)
 * /image_view_1279846165570567012 (http://stair4-basestation:41138/)


As a final test, I tried plugging the camera into the basestation and doing
the same thing. In this case both the basestation AND the laptop
successfully get the image topics, as seen through image_view and the
various rostopic tools.

I don't understand why the messages aren't getting transmitted outbound from
the laptop. It seems everything else works fine, including messages from the
basestation or robot to the laptop. Can anyone see what is wrong with this
or give me places to look?

Thanks!
--Adam






Adam Leeper
Stanford University
aleeper at stanford.edu
719.358.3804
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