Install Telnet Server on Ubuntu

1. Install telnet server (telnetd)

$ sudo apt-get install xinetd telnetd

2. Edit configurations

sudo vi /etc/xinetd.d/telnetd

# paste the bellow configurations
service telnet
{
        disable         = no
        socket_type     = stream
        server          = /usr/sbin/in.telnetd
        protocol        = tcp
        wait            = no
        user            = root
        flags           = IPv6
}

3. Restart xinetd service and verify that port 23 is open

sudo service xinetd restart

# you should see that port 23 is open
sudo netstat -taplun | grep 23
tcp        0      0 0.0.0.0:23              0.0.0.0:*               LISTEN      19755/xinetd

# Get server log
cat /var/log/syslog | grep xinetd