.. _section-FAQs: FAQs ==== * Can I use Wireshark to inspect the user data of my samples? With TypeObject v1, yes. The TypeObject must be included in the discovery packet before the user data packet. See :ref:`section-UserDataDissection` (:numref:`section-UserDataDissection`). With TypeObject v2, user data dissection is not supported. The TypeLookup Service protocol only exchanges types that the remote participant does not already have. When both participants already share the same type, no TypeLookup Service traffic appears in the capture, and Wireshark has no way to reconstruct the type definition needed for dissection. For more details on how TypeObject v2 and the TypeLookup Service work, see :ref:`section-TypeDiscovery` (:numref:`section-TypeDiscovery`). * Why do I see some bytes set to 0 that are not dissected between fields? Those bytes are padding inserted for alignment purposes. * Why can't I see the topic in the dissection of a DATA packet? There is a feature called Topic Information that can show you the Topic's name. (It is disabled by default.) See :numref:`Section-TopicInfo` in this document. * Where can I find more information about the RTPS specification? * RTPS Specification: https://www.omg.org/spec/DDSI-RTPS * DDS Security Specification: https://www.omg.org/spec/DDS-SECURITY * How can I tell when discovery has finished? See `this RTI Knowledge Base article `__. * Can I use Wireshark to inspect data through shared memory? Yes. You can use the |CONNEXT| network capture feature to generate pcap files that include shared memory traffic. See :ref:`section-NetworkCapture` for an overview, or the `Network Capture `__ chapter in the |RTI_CONNEXT| *Core Libraries User's Manual* for full details. * How can I capture traffic being sent through shared memory? Use the |CONNEXT| network capture feature. For details on how to enable and use this feature, see :ref:`section-NetworkCapture` or `this RTI Knowledge Base article `__. * Why is "Decode As" not available for RTPS? Wireshark's "Decode As" feature lets you force a particular dissector for traffic that is not automatically recognized. The RTPS dissector does not need this feature because it uses heuristic detection: it checks the first four bytes of each UDP (or TCP) payload for the RTPS magic number (``RTPS``, 0x52545053). Any packet containing this signature is automatically dissected as RTPS regardless of the port number. If your RTPS traffic is not being detected, verify that the RTPS heuristic dissector is enabled under **Analyze > Enabled Protocols** in Wireshark. * Why can't I see user data in DATA submessages when using Zero Copy? When |CONNEXT| Zero Copy transfer mode is enabled (using FlatData language binding with shared memory), user data is placed directly in shared memory and is not serialized into the RTPS DATA submessage. Instead, the submessage contains only a shared memory reference. This means Wireshark will show the DATA submessage structure, but not the actual user data payload. To inspect user data content in Wireshark, disable Zero Copy transfer mode, or use RTI Admin Console for monitoring Zero Copy applications. See the `Zero Copy Transfer Over Shared Memory `__ chapter in the |RTI_CONNEXT| *Core Libraries User's Manual* for more information.