What Is Port Forwarding & How Does Port Forwarding Work

How Does Port Forwarding Work?

To understand and appreciate port forwarding, you have to know about TCP/UDP ports first. The process is similar to how customer support works. If you’re familiar with Interactive Voice Response (IVRs), you may press 3 to speak with technical support and 4 to speak with the billing department.

Think of your router as an IVR; it knows specific rules and directs you, the caller, to the right place. Like an IVR, your router has specific directives configured in the backend that will perform a similar function, sending internet traffic that is associated with a port number to the specific device on the network that is configured to receive that traffic. (Don’t worry, every packet that hits your router that is intended for your game or server is embedded with the port, so your router will know what to do.)

You should also know that every application uses a specific port number to handle incoming requests from the outside world. For instance, the FTP protocol receives traffic only from port number 21, while the HTTP protocol uses port number 80.

remember our first analogy here , the phone number of a company is the IP address , and the forward request as denote by the number you press when interact with the IVR are the port number .

Whenever you connect to the internet, your internet service provider will assign your device a public IP address. An IP address is just a number (like your house number) that allows ISPs and other networks to recognize you on the internet. But your ISP will assign you a single IP address only; your ISP is pretty oblivious to the fact that you may have WiFi-powered cameras, tablets, 5 computers, and 3 consoles. This is where your router comes in.

When you connect your computer to a WiFi router, which connects to a modem, the router will assign private IP addresses to every single one of your devices (e.g., 192.168.2.33, 192,168.2.92, 192.168.2.221). Your public IP (let’s say it’s 123.45.67.89) address will be the one your ISP assigns you, but your private IP addresses may change.

To simplify thing , look at this to understand the connection :

All connected devices at home < Wi-Fi Router < Modem < Internet Service Provider

Now comes the port forwarding part…

Take the website example here. If you’re hosting a web server, someone trying to access your website will make incoming requests to port 80, the HTTP protocol’s assigned port (unless you happen to be hosting your web server on a different port, but we’re keeping it simple here).

In order for traffic to hit the web server that’s situated behind your router (remember, with 5 computers, 3 consoles, and a bunch of tablets, among other things, how is the router supposed to know which one is the web server?), you need to specify a rule in your router configuration that directs port 80’s traffic to your web server (denoted by its private IP).

Therefore, 123.45.67.89’s web traffic will be directed via the router to 192.168.2.92:80. Without port forwarding, when you tell your two friends to join your Minecraft server using your public IP address, it won’t work. You need to make similar configurations for all the games you play, in fact.

Those configurations put simply, are exactly what port forwarding achieves. It’s a directive that “my webserver gets port 80 traffic” and “my Xbox One gets UDP ports 4500, 3544, 3074-3075, 500, and 88 as well as TCP port 3074 so that I can play Call of Duty: Modern Warfare effectively.” In other words, if you are a heavy gamer and internet geek like we are, you’ll be making a lot of rules like these to divert traffic to the right devices.