Discovery protocol ports

[ChinmayGameti]

Hello,
I have a doubt regarding the Discovery protocol at the OS-abstraction level.
Discovery protocols use some specific ports for the discovery of other publishers or subscribers in the system(using some equation given in OMG DDS standard), and it is only meant to be consumed by the DDS layer. Are these ports accessible to ROS applications are the program level, meaning can a process sniff packets using this port or send packets using this discovery port?

[JLBuenoLopez]

Hi @ChinmayGameti,

You can find information related to this topic in the Listening Locators section in Fast DDS documentation. In ROS 2 you can configure the listening locators using a XML configuration file. ROS 2 does not expose Fast DDS API which can give you the desired information: DataWriter::get_sending_locators and DataReader::get_listening_locators.

Edit: I have been looking into ROS 2 Humble API and the previous methods are exposed in rcl_subscription_get_network_flow_endpoints and rcl_publisher_get_network_flow_endpoints. Also, the native Fast DDS DataWriter is accessible in the RMW layer through the method rmw_fastrtps_cpp::get_datawriter and similarly the DataReader with rmw_fastrtps_cpp::get_datareader method.