Telnet is easiest remote management protocol used in Computer networks. It remains popular even today because of its simplicity. Telnet is a client server protocol where clients uses telnet tool which to connect remote telnet server. This telnet server may be switch, router, windows operating system, linux server or a printer.  In this tutorial we will look how to install and enable telnet with some usage examples.

Install

Ubuntu, Debian, Mint, Kali

We can install telnet package with the following command in deb based Linux distributions.

$ sudo apt install telnet

Fedora, CentOS, RHEL

We can install telnet package with yum command for rpm based distributions like Fedora, centOS and RHEL.

$ sudo yum install telnet

Windows

As windows operating system do not have online package manager telnet is provided by inline. By defualt telnet  server and client applications are not enabled. We will enable the client where server can be enabled too. Follow these instructions.

1. Click Start > Control Panel.
2. Click Programs and Features.
3. Click Turn Windows features on or off.
4. In the Windows Features dialog box, check the Telnet Client check box.

Security

As telnet is old fashion protocol it provides some defects. One of the most important negative issue with telnet is its security features. Telnet do not have any encryption support as builtin. So telnet traffic can be easily eavesdropped during transmission. So do not rely telnet on insecure networks.

Connect Telnet Server

We will start by simply connecting a telnet server. The simplest form is just providing the host name or IP address of the telnet server. The syntax is like below. In this example telnet server is a Ubuntu 17.10 .

$ telnet 192.168.115.143

Connect Different Telnet Port

The default port for telnet is TCP 23 . By default it is not specified during connection. But in some cases telnet server may use different then 23. We can specify the port number by adding after the host name or IP address. In this example we will connect port number 2323 .

$ telnet  192.168.115.143 2323

Specify Login Name

Most cases telnet servers requires authentication. In order to authenticate ourself we need to provide some user name and password. The regular usage is providing username and then put password interactively.  We will use -l which stands for login.

$ telnet -l ismail 192.168.115.143

Interactive Shell

Telnet provides interactive shell where it provides its own environment. We can enter interactive shell just putting telnet command.

$ telnet

We can get help for interactive shell with help command. We can see that we will use open command and the hostname or IP address to connect telnet server.

help

We will connect to the localhost telnet server.

open localhost