but is not activated by default. The server is not part of the default Ubuntu
installation. This is because everything Telnet transmits and receives is in
plain text, including passwords and other sensitive information. Telnet is
generally not a good choice for communication. However, you might want to
install Telnet for certain situations, such as connecting to a piece of equipment
that doesn’t have SSH available—for example, embedded systems where
having a small OS footprint is important and more secure methods of
communication are not available. In addition, sometimes using Telnet is the
quickest and easiest way to test newly installed services during configuration,
such as a Postfix mail server. You might also want to install Telnet to learn
about it and test it simply because you might run across moments in the real
world where no other option exists.
If you decide to install Telnet, use Synaptic or apt to install telnetd,
which installs the server.
Configure your firewall to allow connections through port 23. If this port is
blocked, you cannot use Telnet. See Chapter 20, “Securing Your Machines,”
for help doing this.
After making any needed configuration adjustments to your firewall, type
telnet your IP address to test whether both the client and server are
installed and working by connecting from your terminal using the client back
to the server running on your own computer. You are prompted to enter your
username and password. The whole conversation should look something like
this:
Click here to view code image
matthew@seymour:~$ telnet 192.168.1.102
Trying 192.168.1.102...
Connected to 192.168.1.102 (192.168.1.102)
Escape character is "^]".
Welcome to babbage
Ubuntu 12.04 LTS* All access is logged *login: matthew
Password:
Last login: Sun Jul 4 10:08:34 2012 from seymour
matthew@babbage~$TIP
The server responds with Welcome to babbage, Ubuntu 12.04
LTS, which is a customized message. Your machine will respond similarly.