Registered to the RTPS discovery family behind DDS — but real DDS nodes compute their ports from the domain ID, so 7402 itself is rarely the listener.
IANA reserves 7400-7402 for RTPS, the Real-Time Publish-Subscribe wire protocol that DDS implementations use: rtps-discovery, rtps-dd-ut (user traffic) and rtps-dd-mt (meta-traffic, this port). In practice implementations such as eProsima Fast DDS — the default middleware under ROS 2 — and RTI Connext derive their actual UDP ports from a base plus an offset for the DDS domain ID and participant index, so a scan of a live robotics or industrial fleet shows a spread of ports in the 7400 range rather than exactly 7402. Discovery traffic is mostly UDP, including multicast, so a TCP listener on 7402 is more likely something unrelated squatting the number.
Do not expose
DDS discovery is unauthenticated unless the DDS Security plugins are explicitly enabled; anything reachable on the RTPS ports can enumerate participants, topics and data. Keep it on a trusted segment or a VPN.
$ sudo tcpdump -ni any 'udp portrange 7400-7500'Seen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.