This tool relays specific topics between two different ROS masters.
Run it via:
$ rosrun topic_relay relay /topic http://master1:11311 http://master2:11311The type of the topic doesn't matter, but should be the same on both masters. The behavior of the node is undefined if the types differ. Also, relaying only works when something was already published on both masters.
If on one master, the topic was not yet published, topic_relay will
wait until it got published. In this state, even when the other master
already got its topic, no messages will be forwarded. The moment both
topics are available (i.e., were published on at least once), the
control flow works normally.
Note that the message type on the relayed topic must be installed on
the machine topic_relay runs on (as it calls rosmsg md5 in order
to find the MD5 sum for proper communication with the master).