2 entries are registered on port 502. It is a well-known port (0–1023) — assignments here are IANA's, and a service found on one is usually the service that was assigned it.
services registered on this number
2 transports in use
entries encrypted on the wire
0 of 2 iana-registered
| port | service | proto | category | risk | views |
|---|---|---|---|---|---|
| :502 | Modbus Protocol | TCPUDP | Network Services | caution | 19.2k |
| :502 | Modbus | TCPUDP | Network Services | caution | 13.7k |
Port 502 is primarily associated with Modbus, a widely used industrial automation protocol. It facilitates communication between supervisory computers, controllers, and field devices like PLCs over TCP/IP networks.
port 502 as Modbus Protocol →Modbus is an industrial communication protocol designed to enable communication between devices connected on different types of buses or networks, primarily in automation and control environments. It facilitates data transmission between supervisory computers and devices like PLCs, sensors, and instrumentation, making it a fundamental protocol in industrial control systems.
port 502 as Modbus →The registry says what 502 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 ':502\b'lsof -nP -iTCP:502 -sTCP:LISTENnetstat -ano | findstr :502On 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 502 — 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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