IP Addresses can be Static (constant) or Dynamic (may change randomly)
Find your external IP address (http://whatismyipaddress.com)
You have a router that allows the 3 or 4 computers to share that IP address with the outside world.
If you have the database running on one of your computers with sharing or IWP turned on
A request for your database from outside your local network will go the router. The router is not running the database and the request will fail (with or without error message). If you set the router to forward the request for that port to the computer running the database, outside computers will be able to access the database.
Tell your router to forward port requests for Filemaker to that computer.
If your Internet IP address is 220.127.116.11 and the local computers' addresses are
Computer #1 192.168.0.2 (sharing the filemaker database)
Computer #2 192.168.0.3
Computer #3 192.168.0.4
You tell the router to forward Filemaker port requests to Computer #1 192.168.0.2
thank you very much!