After installing telnetd and xinetd with command

sudo apt-get install xinetd telnetd

Create file telnet and put in /etc/xinetd.d

sudo nano /etc/xinetd.d/telnet

# default: on
# description: The telnet server serves telnet sessions; it uses
# unencrypted username/password pairs for authentication.
service telnet
{
disable = no
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure += USERID
}

Restart xinetd service

sudo service xinetd restart

In xinetd.conf you have includedir /etc/xinetd.d and don't need line

telnet stream tcp nowait telnetd /usr/sbin/tcpd /usr/sbin/in.telnetd

erase it.

In telnet file you can add more option like:

only_from = 192.168.120.0/24 #Only users in 192.168.120.0 can access to
only_from = .bob.com #allow access from bob.com
no_access = 192.168.120.{101,105} #not allow access from the two IP.

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.

3. Then run this script:

   !/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

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/

Regards.