my ($sec,$min,$hour,$mday,$mon,$year) = gmtime(time);
my ($my_port,$my_ip) = sockaddr_in($socket->sockname);
my $me = inet_ntoa($my_ip);
my $hash = sha256_hex("$year$mon$mday$hour$min:$me:$secret");
$socket->send( "TUMBLER1: $hash" );

Example 3: A script named "tumbler" sends the knock.