You can access the file from inside your network because you are (doubtless) pointing your browser to the URL 192.168.2.3. Are you asking your remote friend to do the same? If so, that is what the problem is - the 192.168.2.3 address inside their network does not contain your file.
You have to set up port forwarding on your router (you'll need to read its manual to see how to do that) and port-forward port 591 to your server's address (right now that is 192.168.2.3, but you need to make that fixed, or when you restart your computer your router may allocate it a different address).
Then you have to tell your friend what your router's external address is. This is the public IP allocated by your internet service provider. They will log on to that address, so their router can find your router across the globe. Then the port-forwarding you set up will re-direct that traffic to your Mac that is hosting the file.
If you do not have a static IP address (which you would usually pay a bit extra for, for the convenience) then every so often your ISP will seamlessly change your external address. Then it will not work for your remote friend any more until you tell them what your new public IP address is. You can sign up for a service such as No-ip or DynDNS to get around that problem.