Telnet is an application (protocol) that can be used to manage devices remotely. So if you want to log in to a router, switches or any other device that has a telnet client installed, you can use telnet.
telnet 10.0.0.1 <any specific port/when not specified 23 is the default>Say NO! to telnet!
The reason why telnet it’s almost never used anymore unless the device does not support SSH is that all the messages in a telnet conversation are not encrypted and thus clear-text.
Port testing
Sometimes you see people use telnet to see if a port is open on the remote device. Let’s say you want to know if a web server listens on port 80 you could use:
telnet webserver.domain.com 80But then again, NetCat would be a better alternative because the above method will not work if the protocol you are testing is UDP. (Using the telnet protocol implicitly means you use TCP as the transport layer protocol)
nc -vz webserver.domain.com 80
