Unfortunately, Telnet in Windows is not pre-installed, so you need to install it yourself. Для этого откройте "Control Panel" — "Programs" — "Turn Windows features on or off" or run the command "OptionalFeatures.exe" in a command prompt.

 

When you open the window "Windows features", find in the list "Telnet Client", tick it, press "OK", and it will be installed in the system.

 

telnet

 

Now you can use the program telnet.exe in Command Prompt.