For linux, we used to send one or two EOFs via C-d to the process to
signal exit, however this was inconsistent. Depending on the previous
input from the attacker, sometimes one was needed, sometimes two.
Sometimes, we even observed more than two being needed. Instead, we now
simply loop sending one at a time and checking for the end delimeter.
This will be slightly slower, but avoids hangups or accidentally closing
the shell.
Caleb Stewart