Using Telnet Commands in Linux/Unix

What does Telnet refer to?

Telnet is a dated network protocol employed for establishing connections with remote systems on a TCP/IP network. It operates by connecting to servers and network devices via port 23. Now, let’s examine the application of Telnet commands.

This statement acts as a warning or clarification.

    Do not use Telnet as it is not a secure protocol and is highly discouraged. This is due to the absence of encryption in the transmitted data, making it vulnerable to interception by hackers. Instead, it is recommended to use SSH, which provides encryption and enhanced security.

Let’s explore the process of installing and utilizing the telnet protocol.

Setting up Telnet

In this section, we will guide you on how to install telnet in systems that utilize RPM and DEB.

How to install Telnet on CentOS 7 / RHEL 7

To initiate the installation procedure on the server, execute the command.

# yum install telnet telnet-server -y
Install Telnet Telnet Server
# systemctl start telnet.socket
# systemctl enable telnet.socket
Start And Enable Telnet
# firewall-cmd --permanent --add-port=23/tcp

In the end, you should refresh the firewall so that the rule becomes active.

# firewall-cmd --reload
Allow Port 23 Over Firewall
# systemctl status telnet.socket
Check Status Of Telnet In CentOS 7

Making a login account

In this instance, we will generate a login user for accessing through the telnet protocol.

# adduser telnetuser

Generate a password for the user.

# passwd telnetuser

Please provide the password and confirm it. To log in to a server using the telnet command, use the syntax provided below.

$ telnet server-IP address

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“An instance of this is…”

$ telnet
Logging In To Centos Via Telnet In Putty

How to install Telnet on Ubuntu 18.04?

Executing the command in Ubuntu 18.04 will install the telnet protocol.

$ sudo apt install telnetd -y
Install Telnet On Ubuntu
$ systemctl status inetd
Systemctl Status Inetd
$ ufw allow 23/tcp
Allow Port 23 Over Ufw Firewall
$ ufw reload
Reload ufw Firewall

Using the telnet protocol for verifying the availability of ports.

Using Telnet, you can verify the openness of a particular port on a server by employing the provided syntax.

$ telnet server-IP port

To illustrate, run a command to verify the status of port 22 on a server.

$ telnet  22
Telnet To Test Open Ports

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This tutorial serves as an educational manual explaining how to utilize the telnet protocol. We strongly advise against the utilization of telnet because of the significant security vulnerabilities it presents due to the absence of encryption. When accessing remote systems, SSH is the recommended protocol as it ensures data encryption and protects against potential hacking threats.


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