Passive DDS listening

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Passive DDS listening


I am fairly new to RTI DDS, so I apologize if I do not get the terminology correct. By subscribing to a topic, we are injecting messages into the system. Is it possible to perform a passive listen for messages on a topic?

Thank you very much in advance.


Fernando Garcia's picture
Last seen: 1 month 2 weeks ago
Joined: 05/18/2011
Posts: 200

Hi Kyle,

When you subscribe to a certain topic, DataWriters publishing samples of the topic you are interested in need to be notified of your presence so that those samples can be delivered to your DataReaders. That process is part of the discovery protocol, so you are not injecting messages of the particular topic you want to subscribe to—you are just adding a new DataReader that DataWriters need to send information to. Note that there must be at least one DataReader subscribing to the topic you are interested in, otherwise no samples will be sent on the wire.

If adding a new DataReader to subscribe to the information is incompatible with your requirements, you could potentially sniff the data your applications exchange using tools like Wireshark. In the last few months, Juanjo Martin Carrascosa (an Applications Engineer at RTI) has contributed code to the Wireshark community that makes it simpler to read data samples. These features are available in the latest builds of Wireshark, which you will find in this web page.

Can you describe your requirements so that we can help you figure out the best mechanism to achieve your purpose?