How can EJB's be accessed through Firewalls?
RMI has the ability to tunnel through Firewalls. This is very slow and arduous process, and it is really a security loophole. Special IIOP Firewall Proxies are developed and available that will permit IIOP traffic to pass through. If you are using IIOP protocol, any RMI or CORBA code you write will navigate the firewall.
Limitations are the effectiveness of the proxies. ie you will have to have proxies on both client and server.
IONA provides a proxy called WonderWall and Borland provides the VisiBroker GateKeeper.