Explore subscribed topics

Question

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]{http://www.ros.org/wiki/explore}.

The running node subscribes to :

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

whereas none are written on ros.org.

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

Thanks for answering.

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Originally posted by Erwan R. on ROS Answers with karma: 697 on 2012-06-04

Post score: 0

Answer 1

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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Originally posted by Dan Lazewatsky with karma: 9115 on 2012-06-04

This answer was ACCEPTED on the original site

Post score: 3

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Original comments

Comment by Erwan R. on 2012-06-04:
Thanks ! That brings more light on my way to understanding ROS.

Answer 2

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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Originally posted by Lorenz with karma: 22731 on 2012-06-04

This answer was NOT ACCEPTED on the original site

Post score: 1