Telnet is most likely to be used by system administrators, program developers and anyone who has a need to use specific applications or data located at a particular host computer. It’s a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. Telnet does not installed automatically on CentOS 6.3. You can issue the following command to confirm that telnet is working :

telnet localhost 80

If telnet client does not installed, it should return something like :

[root@centos63 ~]# telnet localhost 80
-bash: telnet: command not found

Issue the following command to install telnet client :

[root@centos63 ~]# yum install telnet -y
Loaded plugins: fastestmirror, presto
Determining fastest mirrors
 * base: mirrors.hostemo.com
 * extras: mirrors.hostemo.com
 * updates: mirrors.hostemo.com
CentOS6.3-Repository                                                         | 4.0 kB     00:00 ...
base                                                                         | 3.7 kB     00:00
extras                                                                       | 3.0 kB     00:00
updates                                                                      | 3.5 kB     00:00
updates/primary_db                                                           | 2.2 MB     00:19
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package telnet.i686 1:0.17-47.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

====================================================================================================
 Package           Arch            Version                    Repository                       Size
====================================================================================================
Installing:
 telnet            i686            1:0.17-47.el6              CentOS6.3-Repository             56 k

Transaction Summary
====================================================================================================
Install       1 Package(s)

Total download size: 56 k
Installed size: 102 k
Downloading Packages:
Setting up and reading Presto delta metadata
Processing delta metadata
Package(s) data still to download: 56 k
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : 1:telnet-0.17-47.el6.i686                                                        1/1
  Verifying  : 1:telnet-0.17-47.el6.i686                                                        1/1

Installed:
  telnet.i686 1:0.17-47.el6

Complete!

If telnet client installed, it should return something like :

[root@centos63 ~]# telnet localhost 80
Trying ::1...
Connected to localhost.
Escape character is '^]'.