[ros-users] How to identify the subscriber or the topic name related to a callback

Jeremy Leibs leibs at willowgarage.com
Fri Feb 4 19:05:35 UTC 2011


On Fri, Feb 4, 2011 at 7:51 AM, Brian Gerkey <gerkey at willowgarage.com> wrote:
> On Fri, Feb 4, 2011 at 12:56 AM, Markus Bader <markus.bader at tuwien.ac.at> wrote:
>> I tried using the connection header but for some reasons the topic
>> field "topic" does not exist!
>> I have: callerid, latching, md5sum, message_definition, type.
>
> I don't know whether "topic" is supposed be in there, but either way,
> the other technique that I described earlier (passing the topic in as
> an extra argument to the callback) will work for you.
>

You're right.  According to http://www.ros.org/wiki/ROS/TCPROS

The topic is only part of the connection_header that the subscriber
sends.  Sorry for the confusion.  On a side-note it feels like it
would be nice to have access to that information in the data structure
though.

>        brian.
>
>> Currently I am using the Ubuntu  10.04 with the default package installation
>>
>> ros::M_string connection_header = event.getConnectionHeader();
>> for ( ros::M_string::iterator it=connection_header.begin() ; it !=
>> connection_header.end(); it++ )
>>        std::cout << it->first << " => " << it->second << std::endl;
>>
>> That code shows me ----------->
>>
>> callerid => /camera0/image_proc
>> latching => 0
>> md5sum => 1b5cf7f984c229b6141ceb3a955aa18f
>> message_definition => # This message defines meta information for a
>> camera. It should be in ...........
>> type => sensor_msgs/CameraInfo
>>
>> Any hints?
>>
>> Greetings
>> Markus
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>>
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