I don't know if you've found an answer yet, I didn't see one here.
Jboss is not a web server, but can be linked to Jetty or Apache / Tomcat (and likely others). Assuming that you're simply working with the Jboss download (ie; no Tomcat), I believe that your question really is "how to configure Jetty to support virtual hosts?"
and you'd use this as a reference in updating your Jetty service under Jboss. Then, each of your Jboss instances will only answer HTTP web requests virtual hosts configuration for that deployment of Jetty.
This will work for HTTP, but you may have to do more to handle your EJBs. For the single IP machine, you'll likely have to configure each Jboss deployment to use different ports (JNDI / RMI / ...).