Dyn.com has been for years a great DynDns service, offering for free this useful service. But this has changed some years ago, when dyn.com started to push its commercial offer. Now, dyn.com forces free users to log in once in a month, otherwise the account and its services is simply deleted. It seems to me absolutely inacceptable and as their paid service is much more expansive that fixed domains or other dyndns services, I decided to change. But to facilitate transition, I want to keep my dyn.com account alive. I found a great script on http://technologicalresolution.blogspot.fr/2013/05/dyndns-auto-logon.html. It was originally designed for Google App Engine, below is a standalone version.

How ?

Just follow the steps below to set up :

1. Download the DynDnsAutoLogin.java file below.
2. Install the java Jsoup library (apt-get libjsoup-java on debian/ubuntu systems, or download it on http://jsoup.org/)
3. Compile the code : javac -cp /usr/share/java/jsoup.jar DynDnsAutoLogin.java (if you downloaded jsoup, you may replace the classpath with the appropriate path to jsoup.jar)
4. Create a DynDnsAutoLogin.properties file, with your username and password ; this file will be search in the working directory while running DynDnsAutoLogin :

DynDnsAutoLogin.properties

You now can launch it yourself :
or add it to your crontab (example here if in your ~/bin path, to run it once a week at midnight) :

Source code

DynDnsAutoLogin.java