FileMaker, Inc. has registered port number 591 with the Internet Assigned Numbers Authority (IANA) specifically for web publishing.
How is your network connected to the internet? DSL or Cable? Provider (Comcast, CenturyLink, etc)?
Some, very few, block ports on their end.
http://www.dslreports.com/ forums can provide info on your provider.
This is a comprehensive guide on the basics
If on a browser on another machine on the local network http://10.0.1.2:593 should open IWP login
http://portforward.com has instructions for many routers (AirportExtreme, not base station)
Test if Your Ports are Open
Now that you have forwarded ports for FileMaker Pro Advanced on the Apple AirPortExtreme you should test to see if your ports are forwarded correctly.
To test if your port has been properly forwarded, you can use our Open Port Check tool. Our Open Port Check tool is the only online port checking tool with Guaranteed Results.
TCP/IP Port Number: The default setting for this is 80. If you do not have any other web services running on your computer then there is little reason to change this from the default setting. But, if you are running Instant Web Publishing on a system that has other services running and there is a conflict with Port 80, then Instant Web Publishing can be configured to use a different port by changing this value. FileMaker, Inc. has registered port number 591 with the Internet Assigned Numbers Authority (IANA) specifically for web publishing.