Your problem is that the person outside your network needs to call the public IP address that the router has. Then you need to tell the router to forward that Filemaker traffic (that calls its Public IP address) on to the private IP address of your computer. It becomes a bit more awkward if the router is assigned a dynamic publci address by your internet service provider - it means that the address is liable to change quite often.
There are websites that will show you what your current public IP address is, but no matter you will still have to have access, and admin rights, to set up port forwarding on the router.
Thank you for answering. If I understand it well, all is needed is to tell the router to forward incoming IWP requests to the IP address showing on the file. Since I do have a dynamic public IP,all I will need to have an outside party look at my files (after the router is set up as you indicated) is to find the public IP address and let them know it? The third party has to call only the public address I give him, not my computer IP, right? Thanks again
Yes, you are right. You need to port-forward requests for Port 591 to the IP address of your computer. If you can tell the remote user the public IP address then they can access the file. As the IP address is dynamic you will have to check it each time.
You can also use a service like DynDNS or no-ip.com to produce the effect of a fixed IP.
Again, thank you for your time and guidance