TNS-12502: TNS:listener received no CONNECT_DATA from client

TNS-12502: "TNS:listener received no CONNECT_DATA from client"

*Cause:  No CONNECT_DATA was passed to the listener.

*Action: Check that the service name resolved from TNSNAMES.ORA has the CONNECT_DATA component of the connect descriptor.

If you getting this error while registering database services with listener using local_listener or remote_listener problem might be with sqlnet.ora and tnsnames.ora setting not implemented by current instance and restarting the instance again after setting TNS_ADMIN parameter might resolve the problem.

Case Study : Implementing TCPS authentication
1. Once you have create all the configuartion and Listener to use TCPS connection and if listener is running on non default port, you would have to set local_listener parameter to register your database with new listener (TCPS). When you creating TNS alias for local_listener, you don't specify connect_data parameter as its not required for service register, however service registration will fail with  TNS-12502 in listener.log until database instance is bounced.
Bouncing/Restarting the instance will read sqlnet.ora , tnsnames.ora with new security config and listener will be able to register the new service on TCPS port.