I assume you only have 1 external IP?
I have had this issue before myself with hosting things at home. The best solution I have found is to use
www.zoneedit.com for DNS hosting. They have a webforward feature that allows you to forward dns entries to new urls.
So I could forward
www.domain.com to
https://www2.domain.com:444This way you can port forward by using the DNS.
If you have a business connection, a better option may be to increase the number of IP addresses that you use. You could then use NAT (if your router supports it) rather then port forwarding.