socket problems

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

i need a way to represent an ip when scanning a c-range for web server info.

use IO::Socket;

my $first_var = "64.219.21.1";
my $last_var  = "25";

my ($net,$first) = ($first_var   =~ /^(\d{1,3}\.\d{1,3}\.\d{1,3})\.(\d
+{1,3})$/ );
die "undetermined network part in $first_var.\n" unless $net;
die "undetermined host part in $first_var.\n" unless $first;

my ($last) = ($last_var =~ /^(\d{1,3})$/ );
die "undetermined host part in $last_var.\n" unless $last;

($last, $first) = ($first, $last) if $last < $first;

my @hosts = ($first..$last);

for ($li=0;$li<=$#hosts;$li++){ &scan() }
[download]

if scan() contains print "$net.$hosts[$li]"; it executes perfectly, printing out all the ip's with no newlines or anything. but let's say this is scan:

sub scan {
    $host = "$net.$hosts[$li]";
    $socket = IO::Socket::INET->new(
        Proto => "tcp",
        PeerAddr => $host,
        PeerPort => 80) or die $!;
        
    $socket->autoflush(1);
    print $socket "HEAD / HTTP/1.0\015\012\015\012";
    
    while (<$socket>) {
        print;
        last if /^$/;
    }
close($socket);
}
[download]

this gives an unknown error. i tried replacing $host with the url "feartech.net" it performed perfectly. so i suppose my question is, how to express the ip in a manner that the connection will go through. thanks for your help.

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Re: socket problems by Aristotle (Chancellor) on Oct 17, 2002 at 01:26 UTC
"An unknown error" isn't good enough. We have no idea what's going wrong from your description. Please use stricŧ and warnings. You're using a subroutine that takes a parameter, but are passing it implicitly using globals - that will get you in trouble sooner or later. Also, you should almost never use the `for(;;)` loop form; use `foreach(LIST)` instead, it avoids so called "fence post" errors (where you do one iteration too few or too many). You're almost doing that with your `@host` variable after all.. Lastly, your parameter passing format - initial IP and terminating last octet - feels pretty awkward (for no reason I could immediately pin down). And choose better variable names than `$first_var` and `$last_var`.. Something like this: `#!/usr/bin/perl -w use strict; use IO::Socket; sub scan { my ($addr) = @_; $socket = IO::Socket::INET->new( Proto => "tcp", PeerAddr => $addr, PeerPort => 80 ) or die $!; $socket->autoflush(1); print $socket "HEAD / HTTP/1.0\015\012\015\012"; print until ($_ = <$socket>) =~ /^$/; close($socket); } my $network = "64.219.21" my @addr = (1, 25); @addr[0,1] = @addr[1,0] if $addr[1] < $addr[0]; scan "$network.$_" for $addr[0] .. $addr[1];` [download] (Untested.) Makeshifts last the longest.	[reply] [d/l]
Re: socket problems by common (Acolyte) on Oct 20, 2002 at 22:21 UTC
unfortunetly active state gave an unknown error when it couldn't connect to the http port of inactive hosts. you can see my confusion then. i believed it was with the way i was inputting my ip. i also corrected my code in many ways thanks to your post, i went for a foreach loop and some other things. thanks.	[reply]