CAn anyone tell me how to open telnet port : 23, manually?

Answer 1

No, you type in telnet xx.xx.xx.xx 23

Where xx.xx.xx.xx is the ip or domain name.

Example:
telnet google.com 23
telnet 127.0.0.1 23

You use a space, not a colon.
Telnet uses port 23 by default so it is not necessary to type in the port number.

Answer 2

The following:

telnet aaa.aaa.aaa.aaa:23 where aaa= the IP address. Follow the IP address with colon23 to specify port 23.

Hope this helps

Answer 3

It depends on what operating system you have.
Its a space if you have linux and a colon if you have windows f I remember right