Verify Portal User Session

I'd like to provide a way for a portal user to link to an outside server without having to log in. I see that Chapter 11 that there is a process for external severs to validate a Rollbase session. Wondering if this approach could work for Portal logins. From the docs... Using Rollbase to Verify Session ID External servers can verify Rollbase session by sending HTTP GET request to specially constructed URL http://rollbase_server/router/servlet/Verify?userId={!#CURR_USER.id}&sessionI d={!#SESSION_ID} If session ID is valid and matches user ID HTTP response will fetch name of server component on which user has opened session: "prod1", "master", etc. Otherwise response may include: ? Invalid: session ID is invalid or no longer active ? Expired: session has expired ? Wrong user: session ID is valid but does not match to user ID ? Error: some error occurred