You need to get the ports open through the firewall to work with the Oracle..
For oracle when database firewall is configured in proxy mode. The clients connecting to the database will use the ezconnect mechanism.
Now here the catch is host and port are of database firewall. Not the actual database host and port information.
You can also add firewall host and port detains in the client side tnsnames.ora for connecting using netalias of the database service.
For more information see: Features Specific to JDBC Thin