My tata wimax connection works well most of the time but it has a supremely annoying feature that to get connected, one is redirected to login in their login site (pretty much how the internet connection works in many hotels). If you are idle for sometime, it will auto logoff. Since my internet connection is not so fast, I usually download over the night and open a keepalive window.

This worked well up until a couple of months back. Now they seem to have decided to disconnect users at random times regardless of internet activity. Not to be deterred by the challenge, I started thinking of how to work around this. The login screen looks like this:

I needed something that keeps logging me in automatically. Qt/WebKit was the obvious choice. It would have been trivial had the post URL of the above form not been dynamic (i.e it has a magic session number in the POST url).

So, here’s what I had to do:
1. Keep loading some website at periodic intervals. Check if I get redirected to their login page. It was a bit tricky to use Qt/WebKit to detect a redirect (in fact, there are two redirects); one has to resort to using timers and check if all the redirection has been done and the pages have been completely loaded.

2. Once the page is loaded I need to get the “dynamic” post URL of the form. I could do a grep in the html but that would be too simple So, I tried evaluateJavaScript that will look in the DOM and return me the post url. Unfortunately, the QVariant returned by evaluateJavaScript() is always null. So, the next strategy was to fill the form details and submit the form entirely using JavaScript. And that worked like a charm

You can find the git repo here (btw, Assembla rocks!).

It struck me later that I probably didn’t need Qt WebKit at all. I think a html/js loading a website periodically in a separate frame and trying to logon if necessary could have worked as well.