Port 1521 — Oracle Database

Port 1521 — TCP

Common port for the Oracle Database listener.

What is port 1521 used for?

Connections to an Oracle Database listener.

Transport protocol

TCP

Security precautions

Apply strict firewall rules for authorized clients and servers.

Should we open this port in the firewall?

Allow this port only when a required service uses it. Apply least privilege: restrict authorized sources, destinations and interfaces, and log connections where appropriate.

How do I check this port?

Test-NetConnection SERVER -Port 1521

On Linux, nc -vz SERVER 1521 checks TCP connectivity only. A successful TCP connection does not validate the application, authentication or TLS configuration.

Port-to-service mappings are common conventions. Applications can use a different configured port; confirm the actual service and transport.