[ros-users] getting a topic's md5sum without subscribing

Eric Berger berger at willowgarage.com
Sat Mar 27 04:52:14 UTC 2010

Have you looked at the topic_tools/relay node?  It should do exactly
what you're talking about already, and you can also use it as an
example of how to implement nodes that handle arbitrary message types.

On Fri, Mar 26, 2010 at 8:08 PM, Ken Tossell <ktossell at umd.edu> wrote:
> Hey ROS,
> I'm working on a node to send messages between other nodes (the proxy
> subscribes to a topic, the publisher sends one copy of a message to it,
> then it forwards the message to several nodes). I need to find the MD5 sum
> of all of the topics so that the proxy can advertise its version of /topic
> as /proxy/topic using the correct signature.
> I had planned to get the MD5 sum using master::getTopics(), but where
> TopicInfo is supposed to have [name, type, md5], getTopics()'s output is
> [name, type, type]. (The underlying RPC doesn't convey the MD5 sum,
> either.)
> Is there any way to determine the MD5 sum of a topic without first
> subscribing to it?
> Thanks,
> Ken
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