I want to redirect a port, so say all traffic coming in on subdomain.xyz.com:2233 is rerouted to an ip 10.13.15.34:3344 (for example) I have access to an ubuntu box if needed, and access to xyz.com's DNS records, but i cannot change the port on the ip. Any help would be appreciated, thanks!
You need to point subdomain.xyz.com to a Linux box you control, and then configure it to DNAT the packets to the server. First add an A record for subdomain.xyz.com pointing to the Linux box. Then setup iptables with something like this: