These are two days that I am trying to find out where this error comes from:
I am trying to reach the database server from an Oracle client based outside the firewall. A TNSPING of the database works fine but a connection with SQLPLUS always brings the same error ORA-12535: connexion timed out.
I have already put the USE_SHARED_SOCKET registry variable to TRUE and reboted the database server.
When looking for you error message in Oracle Documentation, this is what i get :
Cause: The requested connection could not be completed within the timeout period specified by the CONNECT_TIMEOUT parameter in LISTENER.ORA. This error arises from the TNSLSNR.
Action: Either reconfigure CONNECT_TIMEOUT to be 0, which means wait indefinitely, or reconfigure CONNECT_TIMEOUT to be some higher value. Or, if the timeout is unacceptably long, turn on tracing for further information.
Your situation may occur when the routing between your server and the client is not optimal and therefore connection takes longer than your parameter allows it to.