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Perl - Problem writing script to get status of open ports.

Posted on 2008-10-01
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Last Modified: 2013-11-05
Hi,
Some background - I do a lot of vulnerability scanning, and as part of the remediation, when the server admins which reports they have closed, I usually have to manually 'telnet <ip_address> <port>' to see if the port has been closed. Most of these are prod servers, so I cannot just rescan them, but would need to go through a much longer process.

To get around this, I am trying to write a perl script that will do this for me. Basically, I read in the address and port info from an Excel report, and then have tried various methods to try to duplicate the manual telnet process to determine if a port is open or not.

I have tried Net::Telnet, IO::Socket::INET, and a few others that are basically versions of these. I have found that neither produce consistent results, which most often means it's a "me" problem. If someone could point out how I could make this work, or propose an alternate method, I would greatly appreciate it.

I have included a couple snippets to show what I have been trying.

Thanks,
Jeff
.....
use Net::Telnet();
...........
...........
foreach (@hosts)
{
    my $host = $_;
    $telnet = new Net::Telnet();
    $telnet->open(Host => $host,
                  Port => $port);
    $telnet->errmode('return');
    if (($telnet->errmsg eq "") || ( "$telnet->errmsg\n" =~ /^Net::Telnet=GLOB\(0x([0-9a-fA-F]+)\)->errmsg$/ ))
    {
        printf "%s: %s\n", $host, ${\$telnet->errmsg};       #"open";
    }
    else
    {
        printf "%s: %s\n", $host, ${\$telnet->errmsg};
    }
    $telnet->close;
}
***********************************************************************
 
************************************************************************
....
use IO::Socket::INET;
......
.....
            foreach (@hosts)
            {
              my $host = $_;
              $socket = new IO::Socket::INET (
                                              PeerAddr => $host,
                                              PeerPort => $port
                                              );
              if ($socket)
              {
                printf ("%s:%s -- %s\n", $host, $port, "open");
              }
              else
              {
                 printf ("%s:%s -- %s\n", $host, $port, "closed");               
              }
              if ($socket)
              {
                close($socket);
              }
            }

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Question by:jpetter
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Adam314 earned 2000 total points
ID: 22617042
I think for this (just testing if a port is open), the IO::Socket::INET module is probably what you want, not the Net::Telnet module.

What is wrong with the code you are using?  It should work just fine.  You might want to also use the Timeout option.  Also, if you care about the protocol, should specify the Proto option, otherwise IO::Socket::INET will make a guess based on the port.  
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Author Comment

by:jpetter
ID: 22617426
Adam314,

Thanks again for the speedy response. I've added the proto and timeout options, and it seems to be working as expected now....and using the IO::Socket::INET as you recommended.

Thanks,
Jeff
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