I'm trying to kill a screen session. I noticed a lot of other related questions, but none of those answers are working for me. I am trying to kill the following session:

screen -ls

There is a screen on:

    23520.pts-6.porkypig    (09/30/2013 02:49:47 PM)    (Detached)

1 Socket in /var/run/screen/S-root.



screen -r 23520.pts-6.porkypig

Now I am in the session. According to the documentation:

http://www.gnu.org/software/screen/manual/screen.html#Quit

I am supposed to press "control a" and then "control ". I do that and nothing happens.

Another solution said to press Ctrl+a and type :quit. However, again it doesn't do anything. In fact, pressing control+a, absolutely nothing happens afterwards except a message "No Other Window"