I solved the problem by installing Opera browser and add the telnet handler in Opera. Or even better, install Opera and Putty and use Putty to handle “telnet://”. But the problem with Firefox kept bugging me and even if I’m lazy i knew that it became personal.
So I started to search the allmighty internet. I found out that I can add telnet protocol in user prefs in Firefox. But it didn’t work. So I kept searching and finally I’ved put the bits and pieces together and solved the problem. Here it goes.

First thing to do is to tell Firefox that we WANT to use telnet:// links. To do that we must open Firefox and type “about:config” in address bar. And we create a new boolean preference (right click on an empty space), name it “network.protocol-handler.expose.telnet” and set the value “false” and restart the browser. That should be enough for Firefox to let us select an external application to open “telnet://” links.
From this point forward we can choose the easy way and choose putty or the hard way and use gnome-terminal/xterm/konsole. The “hard way” because telnet in terminal doesn’t know how to handle “address:port” format. So how should we do that ? Simple, we create a shell script and we use that script as the default application to open “telnet://” links in Firefox.

The script is pretty easy :

#!/bin/sh

address=`echo ${*##telnet://} | sed 's/:/ /g'`

#For xterm junkies :
xterm -e "telnet $address"

#For gnome-terminal users :
#uncomment the next line but comment
#all other terminal launchers (xterm, konsole)
#gnome-terminal -e "telnet $address"

#For konsole hipsters :
#konsole sends args separately to command so we use "" only for telnet
#uncomment the next line but comment
#all other terminal launchers (gnome-terminal, xterm)
#konsole -e "telnet" $address

And voila, sit back, relax and enjoy a cold beer…