http://localhost/ works but http:/// doesn't

[Ted Anagnost]

http://localhost/ works but http://<ip address>/ doesn't. Internet Explorer

gives a "Cannot find server" message. 

I have tomcat 5.0.18 (without apache).  

I can ping my IP externally. I have port forwarding enabled on my router.

Is there something I need to do to server.xml to enable this to work?  

Thanks