Perl snippet showing how to use netcat (nc) to poll a port, waiting for it to open

netcat_wrapper.pl

# Perl snippet showing how to use netcat (nc) to poll a port,
# waiting for it to open
#
# NOTE: You could also increase the value passed to -w to 60
# to do this, but you wouldn't get an up-to-the minute status
# message printed each second...

my $host = '192.168.1.100';
my $port = '443';
my $MAX_ATTEMPTS = 60; # Number of times to repeat the port check

my $attempt_count = 0;
my $result = undef;

while ($attempt_count < $MAX_ATTEMPTS) {
  $result = system("nc -w 1 -z $host $port");
  exit 0 if ($result == 0);
  print "$host:$port not open.  Sleeping...\n";
  sleep 1;
  $attempt_count++;
}

# If we wound up down here, then give up.
print "$host:$port never opened after $attempt_count attempts.  Exiting 1.\n";
exit 1;