The only way of making your own FFXI server is the following really strange and messy methode:
1: Know your current server TCP/IP address (either will do).
2: Run the playstation or PC version on a locall network, IE use a handy Linux box as your gateway (easiest method really).
3: Add a machine with the static IP of the server on your network OR with the TCP address and be sure your local DNS is used first before the ones your ISP provides.
4: Set up a 'honey' pot server on the Linux box that listens to a range of ports for connections. Check for UDP packets to random Port addresses as well.
5: Find out the login protocol (not hard because it's SENDING the data to you).
After that.. well who knows it would take a number of months before you got more than just the login done I'm sure.
There is another option
1: Set up IP masquerading on the linux box placing a virtual server on it.
2: The virtual server handles forwarding of packets to specific IP addresses while recording the data sent and recieved.
3: This requires a Kernal hack but is still quite doable.
4: This gets you all the information you likely will need for format and data being sent and recieved to the FFX1 server.
The important thing is to have fun
Cyb