Error: "ORA-12541: TNS: no listener" - Spotlight on RAC uses the wrong listener port (4252103)

When trying to connect I get:
ORA-12541: TNS: no listener

In the Verify Cluster Connection Details window I see that the listener port is 1521, but in the used tnsnames.ora file 1525 is configured.

Why does Spotlight on RAC uses the wrong listener port?

Spotlight generates the instance names from a query of v$active_instances (select * from v$active_instances).
Spotlight attempts to match these instances with the instances in the TNSNAMES entry that was specified to connect to the cluster.

If Spotlight finds a match, then it will use the port number specified in tnsnames.ora file. Otherwise it will default to 1521.

If the instance names retrieved from v$active_instances are different to the names in the TNS entry, there is no match, and therefore Spotlight drops back to 1521.

The on-line help entry explains this:

Port
The logical port that is used to access each instance in the cluster. If Spotlight cannot obtain this information from your tnsnames.ora file, it will use the default port number 1521.

The verification dialog has a column called: TNS Entry. You can select a TNS entry from this column to permanently link the instance to a TNSNAMES entry. In this way, if the port changes, and this is reflected in the TNSNAMES file, then Spotlight will automatically pick up the change.

Or you can change the tnsnames.ora file for the cluster entry to use the hostname from the output of select * from v$active_instances.