I don't think mirroring the USB interface is the most straightforward solution to your problem.
I haven't used brltty before; but, from what I understand, you should be able to use tmux to multiplex the terminal outside of brltty altogether.
To be honest, I haven't really used tmux, either; but going from this tutorial...
- start tmux on your master terminal:
tmux -S /tmp/shared
- allow other users to connect to the master:
chmod +r /tmp/shared
- start tmux on your client terminals:
tmux -S /tmp/shared attach -r
The tutorial also gives some suggestions on how to have your client terminals automatically attach to the master terminal on login. That might or might not matter to you; but, if so, you could probably just stick it at the end of the client account's .profile, assuming you don't have any security concerns to worry about.
exec /usr/bin/tmux -S /tmp/shared attach -r
When you press a key or key combination in a terminal, it is transmitted to the application running in the terminal as a sequence of one or more characters. For example, when you press a, the application receives a. When you press Enter, the application receives the character CR (a.k.a. ^M (pronounced “control-emm”), a.k.a. character number 13, a.k.a. \r or \015). Key combinations involving Alt are typically transmitted as the character ESC (a.ka. ^[ a.k.a. \e or \033) followed by the sequence for the key or key combination without Alt. Function keys and other key combinations are transmitted as escape sequences beginning with \e[ or \eO.
The escapes sequences are not fully standardized, and terminals typically ignore certain attributes for certain keys. For example, Ctrl+Shift+letter is often transmitted exactly like Ctrl+letter by default.
You can see what your terminal sends for a key combination by pressing Ctrl+V followed by that key combination in a shell prompt, or C-q or C-h c followed by the key combination in Emacs.
With some terminal emulators, you can configure the escape sequences for each key. On Xterm, this is done through X resources. Most setups read resources from ~/.Xresources when X starts, and you can load the file manually with xrdb -merge ~/.Xresources.
Term.VT100.translations: #override \n\
Ctrl ~Shift ~Meta <key>Return: string("\033[73;5~") \n\
Ctrl Shift ~Meta <key>percent: string("\033[37;6~")
A common convention uses escape sequences of the form ESC [ number1 ; number2 ~ for function keys with modifiers. number1 indicates the function key (15 to 24 for F5 to F12 — for historical reasons, F1 through F4 have different escape sequences) and number2 indicates the modifier (2 for Shift, 3 for Meta, 5 for Ctrl, 7 for Ctrl+Meta, and add 1 for Shift with at least one of Ctrl or Meta).
Emacs translates escape sequences into its internal key representation through input-decode-map or local-function-key-map (or function-key-map before Emacs 23).
(define-key local-function-key-map "\033[73;5~" [(control return)])
(define-key local-function-key-map "\033[37;6~" [(control ?L)])
Best Answer
reptyrversion 0.6 introduced-Toption for "tty-stealing" mode, which works on processes with children.See https://blog.nelhage.com/2014/08/new-reptyr-feature-tty-stealing/ for more details.