A. Telnet is an insecure service. It is recommended that you use ssh service. However sometime telnet server or service is needed. Here are instructions to enable telnet:
Install telnetd server

$ sudo apt-get install telnetd
Restart inetd service:
$ sudo /etc/init.d/openbsd-inetd restart
You should now be able to telnet to the server from Windows or Linux desktop system to Ubentu Linux telnet server. Type the following command to connect to Telnet server:
$ telnet ubentu-linux-server-ip
$ telnet 192.168.1.200
$ telnet ubentu.mydomain.com

Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. Through Telnet, an administrator or another user can access someone else’s computer remotely. On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but not to actually be logged on as a user of that computer. With Telnet, you log on as a regular user with whatever privileges you may have been granted to the specific application and data on that computer.

A Telnet command request looks like this (the computer name is made-up):

telnet namhuy.org

The result of this request would be an invitation to log on with a userid and a prompt for a password. If accepted, you would be logged on like any user who used this computer every day.

Telnet is most likely to be used by program developers and anyone who has a need to use specific applications or data located at a particular host computer.

Install telnetd server

$ sudo apt-get install telnetd

Restart inetd service:

$ sudo /etc/init.d/openbsd-inetd restart

You should now be able to telnet to the server from Windows or Linux desktop system to Ubentu Linux telnet server. Type the following command to connect to Telnet server:

$ telnet ubentu-linux-server-ip
$ telnet 192.168.1.200
$ telnet ubentu.mydomain.com