telnet comes in 2 parts,
- telnet (client)
- telnet-server (daemon, that will by default listen on port 23)
How to Install Telnet in CentOS / RHEL / Scientific Linux 6.4
Telnet is also really useful to check if a certain port on a remote machine is open, here's the format:
$ telnet {ip number} {port number}
For example, to check port 22, we do:
telnet 192.168.52.201 22 Trying 192.168.52.201... Connected to home-directories. Escape character is '^]'. SSH-2.0-OpenSSH_6.6.1
This shows port 22 is open, whereas if we check a port that is closed, e.g. in my case 21, then we get:
[root@openldap-client01 ~]# telnet 192.168.52.201 21 Trying 192.168.52.201... telnet: connect to address 192.168.52.201: Connection refused
also install nmap:
yum install nmap
after that you can check if telnet daemon is listenning on the correct port:
[bash][root@puppetagent1 ~]# nmap localhost
Starting Nmap 5.51 ( http://nmap.org ) at 2014-08-04 02:08 BST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000019s latency).
Other addresses for localhost (not scanned): 127.0.0.1
Not shown: 995 closed ports
PORT STATE SERVICE
22/tcp open ssh
23/tcp open telnet
25/tcp open smtp
111/tcp open rpcbind
631/tcp open ipp [/bash]