Installing telnet client on Linux and Windows Cloud Servers : LayerStack

Telnet is a command protocol that allows a user to connect to a remote host. It makes use of TCP/IP protocol to establish connection with the remote computer.

This command is a valuable tool which allows in troubleshooting and testing of various services in a server. One of the main uses of the telnet command is to check if a particular port is listening on a server. The general format of the telnet command is as below:

telnet [hostname/ipaddress] [port number]

The below example command tests if port 22 is listening for the IP address 123.123.123.123.

telnet 123.123.123.123 22

By default, telnet client is not installed in any Linux/Windows distributions. This guide outlines the general steps to install telnet command in both Linux and Windows servers.

CentOS 6/7/8 & Fedora

Telnet command can be installed using YUM in all CentOS and Fedora distributions.

Execute the below command to install telnet.
```
# yum -y install telnet
```
Verify that the command is installed successfully.
```
# telnet localhost 22
```

Ubuntu & Debian

Telnet command can be installed both in Ubuntu and Debian systems using the APT command.

Execute the below command to install telnet.
```
# apt-get install telnet
```
Verify that the command is installed successfully.
```
# telnet localhost 22
```

Windows OS

If telnet command is not installed in a Windows server, an output similar to below will be received when trying to use telnet.

telnet6

In this situation, telnet command can be installed either through the command prompt or the Server Manager graphical interface.

Installing telnet client through command prompt

To install telnet client, run the below command in the command prompt with administrator permissions.
```
> dism /online /Enable-Feature /FeatureName:TelnetClient
```
Type telnet and press Enter in command prompt, to verify that the command is installed successfully.

Installing telnet client through graphical interface

Server Manager feature can be used to install telnet through graphical interface. For this, follow the below steps.

Open Server Manager.
Click Add roles and features.
Click Next in the Before you begin screen.
In the Installation Type screen, make sure that Role-based or feature-based installation option is selected and click Next.
In the Server Selection screen, select the server in which telnet is to be installed on. By default, the local server should be selected, click Next.
Click Next in the Server Roles screen without selecting anything, since a Windows feature is being installed rather than a role.
In the Features screen, scroll down the list and select the check box next to Telnet Client and then click Next.
On the Confirmation screen, click Install.
Once installation has been completed, a similar screen as below will be displayed. Click Close to exit the wizard.
Type telnet and press Enter in command prompt, to verify that the command is installed successfully.