The six nodes send out one message each when they are done with initialization?
Then my first guess would be that there's some timing issue. Possibilities are e.g.
- The "supervision node" starts listening only after the first messages are already sent
- The three nodes publish immediately after advertising their publisher, before the "supervision node" is completely subscribed
First attempt at a solution: in the six nodes, include a delay of one or two seconds between creation of the publisher and publishing the first message. Start the supervision node first, then the other nodes. If this works, you found your culprit.
Also, you could enable latching:
When a connection is latched, the last
message published is saved and
automatically sent to any future
subscribers that connect. This is
useful for slow-changing to static
data like a map. Note that if there
are multiple publishers on the same
topic, instantiated in the same node,
then only the last published message
from that node will be sent, as
opposed to the last published message
from each publisher on that single
topic.
If both do not work, check if the subscriber and the publishers use the exact same message type. Differences (e.g. publishing std_msgs::Pose, subscribing to std_msgs::PoseStamped) might lead to not receiving anything.
Are all nodes running on the same machine? Network set up correctly?
Yes, same machine.