## Bonus Exercise 1

 1. Bonus exercise!
 2. Implement ‘process pong’. Use ‹socketpair› (see ‹man
    socketpair›) to create a bidirectional communication channel.
 3. Call ‹fork()› to create two processes. The parent process starts
    by writing '.' into the channel.
 4. The processes wait for data to arrive in the channel. When a
    process reads '.' from its end of the socketpair, it prints
    ‘ping’ (if it's the parent) and ‘pong’ (if it's the child).
 5. After writing the message, it sleeps for 1 second, writes '.'
    into the channel and goes back to 4.
