|
|
|
|
# Port Forwarding how to
|
|
|
|
|
|
|
|
|
|
You want to open something on your network to the world.
|
|
|
|
|
|
|
|
|
|
# What is a port
|
|
|
|
|
|
|
|
|
|
Ports solves the problem on how to make many applications communicate over
|
|
|
|
|
the network simultaneously.
|
|
|
|
|
|
|
|
|
|
A port is a number between 0 - 65,535 that gets assigned to any application that wants
|
|
|
|
|
to communicate over the network. This number is then added to every packet
|
|
|
|
|
that is transmitted by that application. The system knows that any respone
|
|
|
|
|
packets with that port number are to be send to that one application.
|
|
|
|
|
|
|
|
|
|
# How firewall works
|
|
|
|
|
|
|
|
|
|
A firewall knows direction and state of traffic.
|
|
|
|
|
|
|
|
|
|
* It allows outgoing communication on any port.
|
|
|
|
|
* But the incoming traffic gets dropped on all ports, unless it is a response
|
|
|
|
|
to communication initialized from the inside.
|
|
|
|
|
|
|
|
|
|
<details>
|
|
|
|
|
<summary><b>More details</b></summary>
|
|
|
|
|
|
|
|
|
|
* When you visit some website you initialize the communication.
|
|
|
|
|
* Your browser picks a random port as the **source port** and sends a request at some IP
|
|
|
|
|
using a well known https port 443 - the **destination port**
|
|
|
|
|
* Then the browser is waiting for a response at that random port.
|
|
|
|
|
* This traffic goes through your firewall and all that info is kept in its state table.
|
|
|
|
|
* This allows firewall to know that when packets start coming from that IP, with that
|
|
|
|
|
source port number now being a destination port, it is a response and let it through.
|
|
|
|
|
|
|
|
|
|
</details>
|
|
|
|
|
|
|
|
|
|
# Port forwarding
|
|
|
|
|
|
|
|
|
|
What if you want to host something, lets say a minecraft server.<br>
|
|
|
|
|
You set it all up, you have your IP address known to others and they try to connect,
|
|
|
|
|
but your firewall blocks them. Its a connection initialized from the outside.
|
|
|
|
|
|
|
|
|
|
So you need to tell your router/firewall to let through traffic that comes to
|
|
|
|
|
minecraft default port - `25565` and where to send it on your LAN,
|
|
|
|
|
to the local IP of your minecraft server.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
### Examples of port forward rule
|
|
|
|
|
|
|
|
|
|
How to actually create that port forward rule depends on router/firewall model.
|
|
|
|
|
It can be easy, it can be bit complicated.
|
|
|
|
|
|
|
|
|
|
Generally what to expect
|
|
|
|
|
|
|
|
|
|
* would be called port forwarding or a virtual server
|
|
|
|
|
* **IP address** is a core information, it is your LAN side machine IP on which
|
|
|
|
|
your stuff runs.
|
|
|
|
|
* Another essential is **the port** on which to expect traffic,
|
|
|
|
|
sometimes called a service port or an external port
|
|
|
|
|
* it might offer option for **internal port**, this can be often left empty
|
|
|
|
|
if port on which your stuff on server is running is the same as the one you
|
|
|
|
|
are opening to the world. But this gives you option to open port 3333 of firewall
|
|
|
|
|
but on your LAN machine have port 80 actually being used.
|
|
|
|
|
* **protocol** - TCP or UDP, if dunno **select both / all**, its safer for the initial setup and testing
|
|
|
|
|
|
|
|
|
|
# Testing if it works
|
|
|
|
|
|
|
|
|
|
### Windows
|
|
|
|
|
|
|
|
|
|
There are sites that will test if your port is open, but you need to run
|
|
|
|
|
some service at that port.
|
|
|
|
|
|
|
|
|
|
* [Port Listener](https://www.rjlsoftware.com/software/utility/portlistener/)
|
|
|
|
|
* [yougetsignal.com](https://www.yougetsignal.com/tools/open-ports/) or
|
|
|
|
|
[portchecker.co](https://portchecker.co/) or
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
### Linux
|
|
|
|
|
|
|
|
|
|
* netcat
|
