use strict;

use warnings;

use Net::DNS;

my $domain      = 'obedience4life.com';

my $resolver    = Net::DNS::Resolver -> new;

my $packet      = $resolver -> query($domain, 'NS');

my @nameServers = $packet   -> answer;

foreach my $rrNameServer (@nameServers)

{

  # We have specifically asked for NS records, but the documentation warn

  # us that the resolver may return other types of records aside from the NS

  # records, so it is important to check each record type.

  next unless $rrNameServer -> type eq 'NS';

  print $rrNameServer       -> string;

}

# This is the output from the above program:

obedience4life.com.     9659    IN      NS      ns1.mvllc.net.
obedience4life.com.     9659    IN      NS      ns1.glacieraudio.com.
obedience4life.com.     9659    IN      NS      ns1.otlamp.com.
        

# Gets or sets the re-transmission interval (in seconds). Default is 5 seconds.

$resolver -> retrans(3);

# Gets or sets the number of times to retry a query. Default is 4.

$resolver -> retry(2);

# Gets or sets the UDP timeout (in seconds). Default is undef which causes

# (retrans * retry) to be used.

$resolver -> udp_timeout(16);

# When TRUE, calls to search, query, and send will print debug info to <STDOUT>.

$resolver -> debug(1);

# Returns a string containing the most recent error message.

my $error = $resolver -> errorstring;

# The resolver will use IPv6 if the libraries are available and if the target

# nameserver is using IPv6. We can force the resolver to use IPv4 like this:

$resolver -> force_v4(1);

# We can use TCP instead of UDP. This is good if our connection is flaky, or

# if answers are too big for a UDP packet. I use UDP as default, and TCP as a

# run-time option to avoid the overhead of open/close of TCP connections.

$resolver -> usevc(1);

# Gets or sets the UDP packet size. Default is the default DNS packet size.

$resolver -> udppacketsize(2048);

# There is an entire subset of methods that perform background operations.

# The resolver can be queried to determine if the operation is complete.

 

# The following code is an outbound email transfer. We will put this together

# with DNS queries in the actual utility. Note that there is no error checking!

 

use strict;

use warnings;

use Socket;

my $mailhost = < MX host IP address expressed in binary >;

my $protocol = (getprotobyname('tcp'))[2];

my $mailport = (getservbyname('smtp', 'tcp'))[2];

 

# Open a TCP socket and name it 'MAIL'.

socket(MAIL, AF_INET, SOCK_STREAM, $protocol);

select((select(MAIL), $| = 1)[0]);  # Unbuffer the socket.

 

# Connect the MAIL socket to the target mail server. S n a4 x8 (below) means:

# S = unsigned short (the protocol), n = a short in network order (the port

# number), a4 = 4 byte ASCII string (packed address), x8 = 8 null bytes.

connect(MAIL, pack('Sna4x8', AF_INET, $mailport, $mailhost));

 

print MAIL "helo $domain\r\n"; # Must use \r\n instead of \n

print MAIL "mail from <$from>\r\n"; # when programming sockets.

print MAIL "rcpt to <$target-user>\r\n";

print MAIL "< your message content goes here >\r\n";

 

# Send the message text as well as any MIME encoded attachments that you may

# have. When you are finished sending data, print a single dot '.' as the first

# character on an otherwise blank line.

print MAIL ".\r\n";

print MAIL "quit\r\n";  # Close the connection to the target mail server.