* check what happens when there are network errors sending the fragments of
  the passwords found.
* the server could store data for statistical purposes (total amount of time
  the clients used to process the work packets, etc).
* look for a way to dinamically adapt the amount of work sent to each client
  to the capacities of the client.
* when the client sends the passwords found, the server should send an ack and
  if the client does not receive it, send the passwords again
* separate djohn's -d in two, one for john-ini's location and another for the
  passwords' location