muaddib2 has asked for the wisdom of the Perl Monks concerning the following question: 


#/usr/bin/perl
use warnings;
use Socket;
print "Ip address ";
my $ipaddr = <STDIN>;
$peer_host = gethostbyaddr($ipaddr, AF_INET);
$peer_addr = inet_ntoa($peer_host);
print $peer_addr;

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This doesn't seem to work and I am not sure why I am getting syntax error

Replies are listed 'Best First'.
Re: DNS Resolution4
by tinman (Curate) on Apr 25, 2001 at 02:58 UTC

    This works for me on Win32 ActivePerl 

    #/usr/bin/perl -w
use strict;
use Socket;
my $host = "www.yahoo.com";
my @addresses = gethostbyname($host)   or die "Can't resolve $host: $!
+\n";
@addresses = map { inet_ntoa($_) } @addresses[4 .. $#addresses];
print "The next set is @addresses \n";

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    No credit to me.. this is a snippet that I got from some book or the other.. but I use it and it works for me

    The following is the complete code for both ways.. 

    #/usr/bin/perl -w
use strict;
use Socket;

my $host = "www.yahoo.com";
my $packed_ip = gethostbyname($host)
    or die "Unable to resolve '$host'\n";
my $ipaddr = inet_ntoa($packed_ip);
print "$ipaddr for $host\n";
my $packed_add = gethostbyaddr($ipaddr, AF_INET);
my $hostname = inet_aton($packed_add) or die "Can't reverse lookup \n"
+;
print "The host name for $ipaddr is $hostname \n";

my $name = "www.perl.com";
my @addresses = gethostbyname($host)   or die "Can't resolve $name: $!
+\n";
@addresses = map { inet_ntoa($_) } @addresses[4 .. $#addresses];
print "The next set is @addresses \n";

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    Try this posting for a much easier way of doing it.. Net::DNS
    Update: Fixed tyop :)
    Update 2: Gave both forward and reverse lookup code

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Re: DNS Resolution4
by hdp (Beadle) on Apr 25, 2001 at 03:45 UTC
    Your code doesn't work because you're passing a hostname to inet_ntoa; it expects an ip address packed into four characters.

    I think you probably misread this example: 

    ($port, $iaddr) = sockaddr_in(getpeername(Socket_Handle));
$peer_host = gethostbyaddr($iaddr, AF_INET);
$peer_addr = inet_ntoa($iaddr);

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    Note that $iaddr, not the return value of gethostbyaddr, is passed to inet_ntoa. What you want can be reduced to a single line: 
    (gethostbyaddr(gethostbyname($ipaddr), AF_INET))[0]

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    hdp.

    p.s. chomp $ipaddr or it'll continue to fail, but in a new and interesting way!

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(boo)Re: DNS Resolution4
by boo_radley (Parson) on Apr 25, 2001 at 02:53 UTC
    well, from the errors that you described, $peer_host is blank.
    since peer_host is set with gethostbyaddr($ipaddr, AF_INET), I changed that line to $peer_host = gethostbyaddr($ipaddr, AF_INET) || die "$!"; so I could see what happens when it dies.
    unfortunately, it just returned "unknown error", so that's not much help.
    I think this may be due to a win32 problem, or something similar. Have you considered checking out IO::Sockets?
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      Is IO::Sockets the same syntax
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Re: DNS Resolution4
by KM (Priest) on Apr 25, 2001 at 21:34 UTC
    I use this little script for checking IPs I get in SPAM headers to make sure I email the correct abuse@* addresses: 

    #!/usr/bin/perl -w

use strict;
use Socket;
my $ip = $ARGV[0] || undef;

unless ($ip) {
    print "What is the IP?\n";
    $ip = <STDIN>;
    chomp $ip;
}

die "No IP given\n" if !$ip;
print "Finding host for $ip...\n";
my $iaddr = inet_aton($ip);
my $name = gethostbyaddr($iaddr, AF_INET) || "NO DATA";

print "$ip is $name\n";

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    Cheers,
    KM

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