If you have a router, to access your machine from outside your LAN you must use port forwarding. Port forwarding applies to external users only - i.e. incoming traffic from outside your LAN. An internet user inside your LAN cannot access your external public IP address and come back in; internal users should access the server on its local internal IP address, or you can set up an alias in a Windows hosts file. This also applies if you are using a URL (web address) which resolves to your public IP address - internal LAN users will not be able to use that URL - the packet is not 'bounced' back into the LAN by the forwarding rules - they apply to incoming external users only.