What are all the things we can do with telnet? [closed]

Question

I would like to know all the things that can be done with telnet, currently i use it to determine if a remote machine is listening on some specific port like this telnet [machine] [port]. any ideas please

Answer 1

Look at telnet as basically opening a socket to another machine on a port.

You can log into another machine (not securely) using it. If you know the SMTP protocol, you can send mail with it. If you know how to formulate an HTTP request, you can even make HTTP requests with it and get back a HTTP response stream. It's a lovely tool.

Answer 2

It can be useful in debugging many application level protocols. For example:

% telnet stackoverflow.com http
HEAD / HTTP/1.1
Host: stackoverflow.com

returns the HTTP headers of stackoverflow.com front page.

Though netcat (man 1 nc) is a bit more versatile in these kinds of tasks.