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Why does `rosnode info <node>` display [unknown type]?

asked 2013-09-05 13:23:47 -0500

updated 2014-01-28 17:17:51 -0500

ngrennan gravatar image

For example -

root@hekateros# rosnode info /hekateros_control
[...removed for brevity...]
  * /hekateros_control/follow_joint_traj_as/goal [unknown type]
[...removed for brevity...]

This message type _should_ be trajectory_msgs/JointTrajectory...

Note that this does not affect the execution of the code (i.e. I can still publish messages of the correct type to this topic, and it works correctly)

I would just like to know why rosnode info is unable to display the correct message type information. Do I need to specify a dependency somewhere? And if so, why does the missing dependency not affect message generation, compilation, or execution?



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answered 2013-09-05 13:46:50 -0500

tfoote gravatar image

rosnode info is querying the master API to get it's information.

Publishers state the topic and type to the master.

Subscribers simply ask for the topic and verify that the type matches when the connection is established with the publisher.

Thus if you only have a subscriber the master does not know what type it is expecting.

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Asked: 2013-09-05 13:23:47 -0500

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Last updated: Sep 05 '13