3 entries are registered on port 1521. 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 3 iana-registered
| port | service | proto | category | risk | views |
|---|---|---|---|---|---|
| :1521 | Oracle TNS Listener | TCP | Security | caution | 19.6k |
| :1521 | Oracle DB Listener | TCP | Databases | caution | 18.4k |
| :1521 | nCube License Manager | TCPUDP | — | safe | 0 |
Port 1521 is commonly used by Oracle Database for its Transparent Network Substrate (TNS) Listener service, which handles incoming client connection requests, database communication, and service management. It's a critical component in enterprise database environments.
port 1521 as Oracle TNS Listener →Port 1521 is the default network listener port used by Oracle Database systems for client-server communications. The listener process manages incoming client connections, routing them to the appropriate database services. It plays a critical role in database connectivity, administration, and high-availability features for Oracle environments.
port 1521 as Oracle DB Listener →Port assigned to the nCube License Manager licensing service.
port 1521 as nCube License Manager →The registry says what 1521 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 ':1521\b'lsof -nP -iTCP:1521 -sTCP:LISTENnetstat -ano | findstr :1521On 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 3 entries above.
A port number is not a service. Anything may listen on 1521 — 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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