-- To fix the finalize problem, I added a part to make each phone book
entry's socket that I closed be null, so select wouldn't check it.
-- Fixed the glibc error that came from closing sockets that had already
been closed on the other end.
-- Added separate function for workers to listen to replies from the exec
server, and took the exec server's socket out of the file descriptor set
in the worker server.
-- Implemented barrier.