Message Oracle ORA-28575 - unable to open RPC connection to external procedure agent

ERRORunable to open RPC connection to external procedure agent
CAUSEInitialization of a network connection to the extproc agent did not succeed. This problem can be caused by network problems, incorrect listener configuration, or incorrect transfer code.
ACTIONCheck listener configuration in LISTENER.ORA and TNSNAMES.ORA, or check Oracle Names Server.