pyddns

The simplest solution for a personal DDNS

One day I received a Raspberry Pi 2 Model B by some friends and I started some experiments with it.

One of the first tasks was a classic: to build a Linux-powered server so I can access my files from outside my Local Area Network. Tipically, one should follow these steps:

1. Install Apache2 or similar into the Raspberry (or whatever)
2. Test if it's accessible from inside the LAN using its local address, like http://192.168.0.100:80
3. Make it reachable from anywhere outside by doing:
   • Port forwarding, so when I type http://<my-external-ip>:<my-port> it's like I'm calling http://192.168.0.100:80
   • Set up a (free?) Dynamics DNS account somewhere so I can forget about IPs and just reach my machine using http://<my-account>.ddns.net

After finishing the last point (by the way, I had a No-Ip account) I realized that... was it that simple?

I already have a personal website on a shared-hosting running PHP, why should I depend on another service (with potential limitations due to a free account)? So here is pyddns!

What does pyddns do?

pyddns makes your current website a real Dynamic Domain Name Server, without efforts. Say you own a website like http://www.example.com, you will end up with the possibility to reach your home server with http://www.example.com/home as it will always point to the most recent IP. The process that maintains the IP updated is automatic.

P.S.: "pyddns" comes from "Pi" + "My" + "DDNS"

How to install it?

First, the requirements:

• An home server (Raspberry? Banana Pi? Traditional PC? ...) running Linux
• A website hosted somewhere capable of running PHP
• 5 minutes of your spare time

There is another fundamental requirement, anyway: your home router must forward the traffic coming from an external port (like 12345) to the internal IP of your home server. There is a guide here.

This project is composed by two folders: /client and /server. We start with the second one: create a folder in your hosted website (e.g. http://www.example.com/home) and upload index.php and ip.txt in it.

index.php is your DNS. When you reach it, it reads the contents of ip.txt, that simply contains the most recent public IP of your home LAN. If it is valid, it redirects you to http://<the-ip>:12345 (the port you opened before) and you will say hurray!

How to maintain ip.txt updated? index.php accepts a POST request in the form "newip=XXX.XXX.XXX.XXX". When it receives that kind of request, it simply overrides the previous IP with the new one given. But who makes this request? The client!

Just open the /client folder, edit the renew-ip.sh file and replace <server-location> with your DNS address (like http://www.example.com/home). Then copy it to your home server in this location: /etc/network/if-up.d. Ensure it is executable using chmod +x renew-ip.sh. This script runs every time the connection is established and fires the POST request to the server.

No more. Goodbye!