sub setnonblocking {
  my $sock = shift;
  # Get the current state of the socket..
  my $flags = fcntl($sock, F_GETFL, 0) or
    die "Can't get the flags on socket: $!\n";
  # ..and then add O_NONBLOCK (nonblocking-ness) on to it.
  fcntl($sock, F_SETFL, $flags | O_NONBLOCK) or
    die "Can't set socket non-blocking: $!\n";
}