If your private server's using the xray client then you do need to do something about the IP the client contacts to be able to play. To find the private server's IP, you could either ask someone from your server, or look in the sclientinfo.xml file. It could be <RO installation>/data/sclientinfo.xml, or it could be in a custom grf under data/sclientinfo.xml. You can find tools for looking in grfs on ratemyservernet. I suggest grftool if you aren't planning to edit the grf; it's MUCH faster than grf factory. As for the IP your client's trying to use, I used wireshark to find mine. I started capturing packets, then ran the client, tried to log in, and paid attention to what IPs were being contacted. The iptables command is listed on Ragnarok Online's appdb entry. But none of this will help until you stop hexing when trying to run the client. That might be the fault of corrupted grfs in your RO installation (either the official or custom ones). Follow normal hex fixing procedures, ie. reinstall the client, make sure you're completely updated (both official and private server updates), bug someone on your private server's forums for help, etc.
