All Oracle errors
TNS-12541net

No listener

TNS-12541: TNS:no listener

Why it happens

Nothing is listening on the host and port in the connect descriptor: the listener is stopped, bound to another port, or a firewall/NAT blocks the connection.

How to fix it

Start the listener (lsnrctl start), confirm its port in listener.ora and the client tnsnames.ora, and test with tnsping. Check firewall rules when the client is outside the database subnet.

A note on TNS-12541

This entry is part of a hand-curated set of ORA-, FRM-, REP- and TNS- codes that actually turn up in production Oracle estates — SQL*Plus, APEX, 19c/21c, ODP.NET apps, Oracle Forms 6i/12c and Reports included. The message text above is the canonical wording; the cause and fix are written in plain language so a developer or DBA can act without digging through pages of Oracle reference docs first.

Codes outside this list of 44 are far less common. If you hit one, the official Oracle error reference and your instance's alert or listener log remain the authoritative source.

Related net errors

ORA-03113 · End-of-file on communication channel ORA-03114 · Not connected to ORACLE ORA-12154 · TNS cannot resolve connect identifier

Build custom software with us

From internal tools to full platforms — we deliver end to end.

Start a Project
Was this tool useful?