I tracked it down to an attempt to put the socket in non-blocking mode in IO::Socket:

$blocking = $sock->blocking(0) if $timeout;

[download]

blocking returns undef. (But $! is not set. Does that mean that switching to non-blocking didn't fail? The docs define failure as returning undef and setting $!.) The timeout mechanism relies on using non-blocking mode, and the results are consistent on this method failing or the following connect ignoring the non-blocking mode.

I wish I could go deeper -- does Perl simply ignore non-blocking on sockets in Windows, or does Windows not support it -- but I'm not sure how.

Update: Here's a cleaned up version of the program I used to test my assertions:


use strict;
use warnings;

use IO::Socket;


sub show_blocking_result {
   my ($blocking) = @_;

   die("Error switching to non-blocking: $!\n")
      if not defined $blocking;

   printf("Was previously: %s\n",
      ($blocking ? "blocking" : "non-blocking"),
   );
}


my $sock = new IO::Socket::INET(
   PeerAddr => "www.perlmonks.org",
   PeerPort => 80,
   Proto => 'tcp',
);

die("Error connecting: $!\n")
  if not defined $sock;

# We didn't turn off blocking mode,
# so the following should return true.
show_blocking_result($sock->blocking(0));

# Should return false, but presumably defined.
show_blocking_result($sock->blocking(1));


__END__

Windows
-------
Error switching to non-blocking:

FreeBSD
-------
Was previously: blocking
Was previously: non-blocking

[download]

In reply to Re: nbtstat.pl fails for non-windows IP by ikegami
in thread nbtstat.pl fails for non-windows IP by sgrey

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.