## Exercise 6

Do what ‹nc -l› does, but only in one direction and using UNIX
domain sockets:

 1. listen on a socket given by the first argument,
 2. when a client connects, copy anything it sends to your standard
    output,
 3. exit when the client disconnects.

You can use ‹nc -U socket› to test, or you can use your own program
from the previous exercise.
