Sounds like the job of a web service of some sort to act at the intermediary.
Portlets can access any
J2EE resource that is supported by your server - JMS,
JDBC, web services, RMI/IIOP. All you need to know is how to code for them.
So, how would you access this external resource in a
Servlet? That's probably the same way you'd access it from a Portlet.
Make sense?
-Cameron McKenzie