What is Telnet ?

Telnet is an old network protocol that is used to connect to remote systems over a TCP/IP network. It connects to servers and network equipment over port 23. Let’s take a look at Telnet command usage.

Disclaimer

  1. Telnet is not a secure protocol and is thus NOT RECOMMENDED!. This is because data sent over the protocol is unencrypted and can be intercepted by hackers.
  2. Instead of using telnet, a more preferred protocol to use is SSH which is encrypted and more secure

Let’s see how you can install and use the telnet protocol.

Installing Telnet

In this section, we will walk you through the process of installing telnet in RPM and DEB systems.

Installation of Telnet in CentOS 7 / RHEL 7

To begin the installation process on the server, run the command

Sample Output

install-telnet-telnet-server

Next, Start and enable the telnet service by issuing the command below

Sample Output

start-and-enable-telnet

Next, allow port 23 which is the native port that telnet uses on the firewall.

Finally, reload the firewall for the rule to take effect.

Sample Output

To verify the status of telnet run

Sample Output

Telnet protocol is now ready for use. Next, we are going to create a login user.

Creating a login user

In this example, we will create a login user for logging in using the telnet protocol.

Create a password for the user.

Specify the password and confirm.

To use telnet command to log in to a server, use the syntax below.

For example

In the black console, specify the username and password.

useradd-expiry

Installation of Telnet in Ubuntu 18.04

To install telnet protocol in Ubuntu 18.04 execute:

Sample Output

check-status-of-telnet-in-CentOS-7

To check whether telnet service is running, execute the command.

Sample Output

Next, we need to open port 23 in ufw firewall.

Sample Output

allow-port-23-over-ufw-firewall

Finally, reload the firewall to effect the changes.

Telnet has been successfully installed and ready for use. Like in the previous example in CentOS 7, you need to create a login user and log in using the same syntax.

Using telnet to check for open ports

Telnet can also be used to check if a specific port is open on a server. To do so, use the syntax below.

For example, to check if port 22 is open on a server, run

Sample Output

telnet-to-test-open-ports

Summary

This tutorial is an educational guide that shows you how to use telnet protocol. We HIGHLY DISCOURAGE the use of telnet due to the high-security risks it poses due to lack of encryption. SSH is the recommended protocol when connecting to remote systems. The data sent over SSH is encrypted and kept safe from hackers.

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