why "stty -echo" exits from ssh

[mocore]

sshing into a box running tc ...
then running "stty -echo"
eg

   ( '>')
  /) TC (\   Core is distributed with ABSOLUTELY NO WARRANTY.
 (/-_--_-\)           www.tinycorelinux.net

tinycore@pc:~$ stty -echo
Connection to *ip-address* closed.
ob@otherbox:~/

causes  exit from ssh
presumably something to do with  still somewhat mystic tty ...
see also :" the TTY demystified " @ https://forum.tinycorelinux.net/index.php?topic=27406.0


background , trying (to copy) various methods[2] to capture key press in script (awk)
i found "stty -echo" appeared to be used to prevent "asci control characters"
from being echoed

eg

awk 'function cmd(str){ cmd_str=( str == "" ? "echo foo" : str) ; while( (cmd_str | getline line) >0 ) print line  }
BEGIN{ cmd("clear"); while(1) { getline xline < "/dev/tty" ; print  xline ; } }'

run the above infinite loop
then pressing
>up down left right
arrow keys
*should* show

^[[A^[[C^[[D^[[C

** use ctrl-c to exit the process ( though id assume that is obvious to most readers !)

Code: [Select]

awk 'function cmd(str){ cmd_str=( str == "" ? "echo foo" : str) ; while( (cmd_str | getline line) >0 ) print line  }
BEGIN{ cmd("clear;stty -echo"); while(1) { getline xline < "/dev/tty" ; print  xline ; } }'

adding (the mystical) command "stty -echo" to the command indeed prevents this echoing ;
when run locally

can any more knowledgeable mystic explain
what magic it is exactly
which makes  "stty -echo" exit from ssh? ?.?.?


**[2]

comparing
key-press methods from fm.awk and

https://jellepelgrims.com/posts/awkventure
 https://github.com/jpelgrims/awkventure