I am running Ubuntu 14.04 in VMWare Player with a bridged Adapter. I installed another VM in Ubuntu which can be accessed from Mozilla Firefox. The web page opens but when I click certain links in that webpage (which require telnet client to open automatically) no client opens and Firefox gives the error:

The address wasn't understood

Firefox doesn't know how to open this address, because one of the following protocols (telnet) isn't associated with any program or is not allowed in this context.

You might need to install other software to open this address.

Whereas I have installed putty in Ubuntu...

These addresses are of the format telnet://:xxxx

Waiting eagerly for your kind reply.


This is a known issue with Mozilla Firefox running on Ubuntu for amd64 systems. The correct solution is:

1.open Firefox and type “about:config” in address bar

2.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.

  1. Then run this script:


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

For furthur refrences : http://ccielab.ro/2009/11/telnet-handler-in-firefox-kubuntu/ http://www.tolaris.com/2010/08/23/enabling-telnet-and-ssh-urls-in-firefox-for-linux/



Maybe is not first class solution but you can try this add-ons

You will be able to define preferred app for open telnet link ...


This computer error may be caused by the lost of system files. You can try to restore your computer or you can download a WiseRecoveryto help you. WiseRecovery helps me fix the same computer problem for me. If you have not find the proper methods, you can try it.

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