I need to add another secure instance of Tomcat in a server that already uses port 80 and port 433.
Is there any way to hide the port number of the new instance, since I'll need to use one which is not universally accepted?
Thanks in advance.
No, there's no way to hide the port number. Do you have apache running on 80/443? If so, what I'd recommend is to create a new name-based VirtualHost for the tomcat app, and use apache's mod_proxy to proxy through to whatever port tomcat is listening on.
Here's a quick tutorial on how to set up mod_proxy.
Probably the simplest and quickest option is to use a DNAT. You would configure an additional Internet routable IP and NAT the traffic on standard ports to your additional instance. This would be done on your router.
If you have a single server bound to Internet routable IPs, you could bring that additional IP up on the server and bind Tomcat to that, which would allow it to listen on standard ports if they were not used by something else.
If you have a proxy or load balancer, you can potentially configure VIPs or interfaces on them as well.