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asked 2012-06-04 05:01:34 -0500

Erwan R. gravatar image

Hello !

I'm currently investigating deeper into explore node as it drives (in simulation) my PR2 to discover his environment. When running the node and looking at rxgraph, I noticed that the subscribed topics differs from the ones listed in the [documentation]{}.

The running node subscribes to :

  1. /move_base/result
  2. /move_base/feedback
  3. /move_base/status
  4. /tf

whereas none are written on

Is that because of a node update and what are they used for ?

Thanks for answering.

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answered 2012-06-04 05:06:02 -0500

updated 2012-06-04 07:53:25 -0500

1-3 are the result of an action interface (more information about actionlib).

4 is the result of a tf listener.

All of the above are features of ROS that use topics to communicate, but don't require explicitly creating publishers or subscribers, and are not considered part of a node's topic API.

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Thanks ! That brings more light on my way to understanding ROS.

Erwan R. gravatar image Erwan R.  ( 2012-06-04 05:19:47 -0500 )edit

answered 2012-06-04 05:08:20 -0500

Lorenz gravatar image

The subscription to tf is pretty common, every node that instantiates a tf::TransformListener subscribes to it, so I don't think it is part of the API and needs to be mentioned in the documentation.

The subscriptions to the move_base topics is actually mentioned in the documentation at section 2.1.4. Every action client subscribes to the result, feedback and status topic of the action server and publishes the goal and the cancel topic.

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Asked: 2012-06-04 05:01:34 -0500

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Last updated: Jun 04 '12