2 entries are registered on port 4840. It is a registered port (1024–49151) — IANA records an assignee, but nothing stops other software from listening here, which is why the number carries more than one entry.
services registered on this number
2 transports in use
entries encrypted on the wire
2 of 2 iana-registered
| port | service | proto | category | risk | views |
|---|---|---|---|---|---|
| :4840 | OPC UA TCP | TCPUDP | Network Services | caution | 26.6k |
| :4840 | OPC UA PubSub over UDP | UDP | Network Services | caution | 0 |
OPC Unified Architecture (OPC UA) is a machine-to-machine communication protocol for industrial automation developed by the OPC Foundation. It is designed to facilitate the secure and reliable exchange of data in industrial control systems, supporting complex data modeling while remaining platform-independent.
port 4840 as OPC UA TCP →OPC UA PubSub UADP datagrams carried over UDP multicast for industrial telemetry and control.
port 4840 as OPC UA PubSub over UDP →The registry says what 4840 is registered to. What is listening on it right now is decided by the host, and only the host can be asked. Each of these prints the process behind the socket.
ss -ltnp | grep ':4840\b'lsof -nP -iTCP:4840 -sTCP:LISTENnetstat -ano | findstr :4840On Linux and Windows the process name comes back with the socket; on macOS lsof needs sudo to name a process that isn't yours. Match what it prints against the 2 entries above.
A port number is not a service. Anything may listen on 4840 — what you actually met is decided by the host, not the registry. If a service is missing here, it belongs in the registry.
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