Specifications

telnet
20
 To break the attempted connection, press the Ctrl+Shift+6 keys and then the B key.
Other escape sequences are not supported.
 This command sends the input key codes to the login destination host without
making any modifications. Therefore, the key code used on the terminal on which
this command is entered must be the same as the key code recognized by the
destination host. If they are different, the command will not operate correctly. For
example, as the input key code for the Enter key, some terminals generate only CR,
whereas other terminals generate CR and LF. Also, when a destination device
recognizes the Enter key, some devices only recognize CR, whereas other devices
recognize CR and LF. Check the settings of the input terminal and the login
destination device beforehand.