cant use sockets in win32 perl

Posted on 2006-10-24
Last Modified: 2010-05-18
win32 perl 5.8.8

trying to use IO::Sockets to open up a tcp connection, to just do a simple communication between two computers on the same subnet.

first i run the receiver on one computer:

use IO::Socket;
my $sock = new IO::Socket::INET (
                                 LocalHost => '',
                                 LocalPort => 9000,
                                 Proto => 'tcp',
                                 Listen => 1,
                                 Reuse => 1,
die "Could not create socket: $!\n" unless $sock;
my $new_sock = $sock->accept();
while(<$new_sock>) {
   print $_;

with the intention of running the sender on another computer


use IO::Socket;
my $sock = new IO::Socket::INET (
                                 PeerAddr => '',
                                 PeerPort => 9000,
                                 Proto => 'tcp'
die "Could not create socket: $!\n" unless $sock;
print $sock "Hello there!\n";


but the receiver never connects, always dies with a "could not create socket:  Unknown error" message

what am i doing wrong?
Question by:jephtah
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Author Comment

ID: 17800441
if i change both hostnames to "localhost" and do it all on one computer (two terminal windows), it works correctly.

if i change peer address to "" and peer port to 80, it sends my little packet to yahoo, and i get back a 'bad html request' answer from them.

i think maybe i dont have my computers set up to accept traffic on the ports correctly or something...   i am behind my company's firewall, but being on the same subnet, it shouldnt matter.  in fact, both computers are physically sharing the same switch port, via a simple hub.  i tried to set ports open on my network settings, but apparently it didnt do what i hoped it would do.

LVL 25

Expert Comment

ID: 17800627
You probably have XP SP2 installed and the firewall enabled.
LVL 18

Accepted Solution

Morcalavin earned 125 total points
ID: 17802840
Take this out:
LocalHost => '',

Not defining the localhost will allow the server to listen for incoming calls on the socket from any ip address.
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Author Comment

ID: 17813750
i do not have the firewall enabled.

Author Comment

ID: 17813926

ok, that works, but i dont understand why the LocalHost has to be removed.  all of the examples for IO::Socket specify a LocalHost.  

LVL 18

Expert Comment

ID: 17813954
I'm not entirely sure as I'm not a socket genius, but I had this same problem in a perl socket program and a c# socket program.  Specifying the localip address as your localhost would only allow you, the localhost, to send to the socket.  I guess localhost defines the server your listenting for, not what server you are listening on.  *shrugs*

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