Tell screen how to deal with user interfaces (displays) that cease to accept output. This can happen if a user presses ^S or a TCP/modem connection gets cut but no hangup is received. If nonblock is
off(this is the default) screen waits until the display restarts to accept the output. If nonblock is
on, screen waits until the timeout is reached (
onis treated as 1s). If the display still doesn't receive characters, screen will consider it “blocked” and stop sending characters to it. If at some time it restarts to accept characters, screen will unblock the display and redisplay the updated window contents.