Sometimes,( at the risk of exposing your computer to the big bad world), you want to allow access from the internet to an application running on your P.C.
Your P.C is usually going to be behind a router, so the internet knows only the address of the router and not your P.C. Your router is keeping your internal network separate from the internet. The router has two I.P.s, an internal one to communicate with the internal network, and an external one to communicate with the internet.
You also should have a firewall setup on your router to not allow any incoming traffic to your internal network.
But suppose you do want to expose an application on your P.C. to the internet, how to go about it ?
The internet knows only the router's external I.P. So obviously, that has to be used.
We need to configure what is called "Port Forwarding" on the router. What it allows us to do is redirect an incoming request to the router on a particular port to the same/another port on some machine in the internal network.
So for example, i might setup forwarding such that a request to http://router-external-ip:8080 is redirected to my P.C 192.168.1.200:80, thus making my application running at 192.168.1.200:80 available to the internet.
Note that the firewall rules may have to be changed to allow the incoming traffic, preferably restricted to the external address making the request, and the port being used.
There are sites online that will allow you to test whether the port forwarding is working or not, e.g. https://www.yougetsignal.com/tools/open-ports/
If you are getting connection refused errors, check that the firewall on the P.C allows the incoming call, as well as the firewall on the internet host that is making the call. E.g if its hosted, the hosting provider may have opened default ports like 80, but blocked others like 8080 for outgoing calls.
Your P.C is usually going to be behind a router, so the internet knows only the address of the router and not your P.C. Your router is keeping your internal network separate from the internet. The router has two I.P.s, an internal one to communicate with the internal network, and an external one to communicate with the internet.
You also should have a firewall setup on your router to not allow any incoming traffic to your internal network.
But suppose you do want to expose an application on your P.C. to the internet, how to go about it ?
The internet knows only the router's external I.P. So obviously, that has to be used.
We need to configure what is called "Port Forwarding" on the router. What it allows us to do is redirect an incoming request to the router on a particular port to the same/another port on some machine in the internal network.
So for example, i might setup forwarding such that a request to http://router-external-ip:8080 is redirected to my P.C 192.168.1.200:80, thus making my application running at 192.168.1.200:80 available to the internet.
Note that the firewall rules may have to be changed to allow the incoming traffic, preferably restricted to the external address making the request, and the port being used.
There are sites online that will allow you to test whether the port forwarding is working or not, e.g. https://www.yougetsignal.com/tools/open-ports/
If you are getting connection refused errors, check that the firewall on the P.C allows the incoming call, as well as the firewall on the internet host that is making the call. E.g if its hosted, the hosting provider may have opened default ports like 80, but blocked others like 8080 for outgoing calls.
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