The word “telnet” often refers to the Telnet client, since the command to run the client has the same name as the protocol. This page is about the telnet client which we use in this guide to test and debug servers.
Telnet is a computer protocol that was built for interacting with remote computers ([IETF RFC-854]: https://tools.ietf.org/html/rfc854).
Telnet utility allows users to test connectivity to remote machines and issue commands through the use of a keyboard, and one of the simplest ways to check if a port is open and listening on a network.
How to install
Debian / Ubuntu Linux
sudo apt-get update && sudo apt-get install telnet
Fedora, CentOS, RedHat
sudo yum install telnet
brew install telnet