JDBC Adapter connection through firewall

Hi guys,

I was wondering if there is any information available regarding a JDBC Connection (JDBC Adapter) through a firewall. We are experiencing some issues with the connections. We are connecting from the internal network to the DMZ. Access on the DMZ has been granted for the internal server. We have tried both THIN and OCI and opened ports 1521 (Oracle Listener) and 1610 (Connection Manager).

A normal SQL*Net connection (SQLPlus) works fine, just not from the IS.

Are there any other known settings that need to be applied to make a JDBC Connection through a firewall (Cisco PIX)?