docs: prerequisites, fixes #1

Author: richardschneider

doc/articles/gotchas.md

@@ -17,7 +17,11 @@ It uses the following protocols to create a public IP address
 - [RFC 6886 - NAT Port Mapping Protocol](https://tools.ietf.org/html/rfc6886)
 
 > [!WARNING]
->  NAT Port Mapping Protocol is not fully implemented.  See [issue #3](https://github.com/richardschneider/net-nat/issues/3).
+>  NAT Port Mapping Protocol is not fully implemented.  See [**issue #3**](https://github.com/richardschneider/net-nat/issues/3).
 
-Use the [natcheck](natcheck.md) tool to examine your network environment. See the [gotchas]()
-for reasons why things fail.
+> [!NOTE]
+> Please read the [**Prerequisites**](prerequisite.md) article, before running the software.
+
+## NAT checker
+
+Use the [natcheck](natcheck.md) tool to examine your network environment.

doc/articles/intro.md

@@ -0,0 +1,27 @@
+# Prerequisites
+
+The net-nat package requires other network components to be configured.
+
+## Router
+
+Your router must be configured to be a NAT that performs port forwarding to your computer.
+As each router has a different administration UI, you will have to read the guide on your
+router.  
+
+Here's a good article on [port forwarding](https://www.howtogeek.com/66214/how-to-forward-ports-on-your-router/).
+
+## Firewall
+
+If your computer has a firewall (for example Windows Defender), you must also 
+configure the firewall to open your local port.
+
+Here's a good article on configuring [Windows Defender](https://www.howtogeek.com/394735/how-do-i-open-a-port-on-windows-firewall/).
+
+## HTTP
+
+If you are forwarding HTTP requests, then on Windows, `HTTP.SYS` must be configured to allow incoming requests
+on port 80.
+
+```console
+> netsh http add urlacl url="http://+:80/" user="Everyone"
+```

doc/articles/prerequisite.md

@@ -5,14 +5,14 @@
       href: usage.md
     - name: Server Example
       href: server.md
+- name: Prerequisites
+  href: prerequisite.md
 - name: NAT Discovery
   href: discovery.md
 - name: Public Address
   href: pubaddr.md
 - name: NAT Check
   href: natcheck.md
-- name: Gotchas
-  href: gotchas.md
 - name: Class Reference
   href: ../api/Makaretu.Nat.yml