Connection error while connecting to Oracle XE
The ORA-609 error is thrown when a client connection of any kind failed to complete or aborted the connection process before the server process was completely spawned. Beginning with 10gR2, a default value for inbound connect timeout has been set at 60 seconds.  This is also triggered when a DB session is killed/aborted manually from the OS prompt.  
  
  To remove a primary ORA-609 error, you should increase the values for INBOUND_CONNECT_TIMEOUT at both listener and server side sqlnet.ora file as a preventive measure. If the problem is due to connection timeouts, and increase in the following parameters should eliminate or reduce the occurrence of the ORA-609 error.
  
  
  Sqlnet.ora: SQLNET.INBOUND_CONNECT_TIMEOUT=180
  Listener.ora: INBOUND_CONNECT_TIMEOUT_listener_name=120
  


Reference
See: ORA-609 opiodr aborting process unknown ospid tips (Burleson Consulting)