These URL schemes are defined in RFC 1738, and are used for logging in via a terminal emulator. They have the form
telnet://user:password@host:port
but the password component is ignored.
To handle rlogin, telnet and tn3270 URLs, a rlogin,
telnet or tn3270 (the program names and arguments are
hardcoded) session is run in a terminal-emulator buffer.
Well-known ports are used if the URL does not specify a port.