Internet-Security.com TCP port 684 details

TCP port 684 is the IANA-registered port for CORBA IIOP over SSL (IIOP/SSL).
It is used by CORBA middleware/ORBs such as TAO, OmniORB, and ORBexpress, which implement secure IIOP and in some deployments expose it on 684.
Enterprise app servers that support IIOP/SSL (e.g., IBM WebSphere Application Server’s RMI-IIOP/SSL and Oracle WebLogic’s IIOP/SSL) also support this protocol and can be configured to listen on 684, though many installations use vendor-specific ports.

TCP 684