Exercise 3: Ending Sessions and Cleaning Up Dead Ones — Possible Solution
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End "web" cleanly, without attaching:

  screen -S web -X quit
  screen -ls                 # web no longer appears

Now kill the db server process forcibly (using the PID from -ls):

  kill -9 31022
  screen -ls

The db line is still listed, but marked as dead, for example:

          31022.db    (Dead ???)

The process has gone, but its socket file in the screen directory was
never removed, because the server had no chance to clean up.

Clean up:

  screen -wipe

This removes the dead socket and reports what it removed. Running
screen -ls again shows db has gone.

WHY THIS WORKS AS AN ANSWER
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It contrasts an orderly shutdown (-X quit, which removes the socket
itself) with a forced kill (which leaves a dead socket), explaining
why "Dead" sessions exist and why kill -9 should be a last resort.