sub play_remote_file
{
   my $file = shift;

   my $sock = new IO::Socket::INET (PeerAddr => 'jcwren',
                                    PeerPort => 10666,
                                    Proto    => 'tcp',
                                   );

   return unless $sock;

   print $sock $file, "\n";

   $SIG{ALRM} = \&timed_out;

   eval {
       alarm (30);
       my $buf = <$sock>;
       alarm (0);
   };

   close ($sock);
}

sub timed_out 
{
   die "GOT TIRED OF WAITING";
}
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Yes, I see that, but what would happen if
you called this code with a valid,unreachable
IP address (e.g. 127.0.0.2) ?

My problem is that my program hangs at the connect,
and I want that forced out...
I know IO::Socket::new times out pretty quickly when
the remeote system's port I want to reach is closed,
but I find it hanging when the system does not respond
at all.

GrtZ!,


ChOas

I think you are hitting a bug in Perl. I believe that Tom May nailed it. I think that it has been "fixed" for some definition of fixed, but judging from this the fix is probably not going to make you happy. The actual patch is here. Judging from that you need IO::Select available with a "blocking" method to do timeouts properly.

I don't have time to pursue this further, but I think that anyone who wants to get their hands dirty with Perl is likely to find getting blocking working on your platform to be a good place to get your feet wet.

#!/usr/local/bin/perl -w

use strict;
use IO::Socket;

{
   my $timeout = 0;
   my $sock = undef;

   $SIG{ALRM} = sub {$timeout = 1; die};

   eval {
         alarm (2);
         $sock = new IO::Socket::INET (PeerAddr => '10.1.1.18',
                                       PeerPort => 29,
                                      );
         alarm (0);
        };

   die "Can't open socket: timeout=$timeout\n" if ($timeout or !$sock)
+;

   print "I would print to the socket now, if I knew what I was connec
+ted to\n";

   close ($sock);
}
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#!/usr/local/bin/perl -w

use strict;
use IO::Socket;

{
   my $sock = undef;

   $SIG{ALRM} = sub {die "GOT TIRED OF WAITING"};

   eval {
         alarm (2);
         $sock = new IO::Socket::INET (PeerAddr => '10.0.0.18',
                                       PeerPort => 29,
                                      );
         alarm (0);
        };

   die "Can't open socket: $@\n" if (!$sock);

   print "I would print to the socket now, if I knew what I was connec
+ted to\n";

   close ($sock);
}
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#!/usr/bin/perl -w

use strict;
use IO::Socket;


die "Usage: <IP address> <Port>\n" unless (scalar @ARGV==2);

my $Status="Failed";
my ($Host,$Port)=@ARGV;

my $Socket=IO::Socket::INET->new("$Host:$Port");

$Status="Okay" if $Socket;

die "Everything $Status\n";
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Have you considered pinging (Net::Ping) the host first to make sure it is alive before you enter the IO::Socket section of your code? It may be much easier than handling the connection timeout the way you want to.

Net::Ping would be a problem on UNIX machines. ICMP pings require the script to be run as root. Windows users won't have the same problem.

You could either try to patch your local version of Net::Ping to disable the root requirement, or use backticks or system to execute the ping.

Hubris time here. I think everyone has missed the problem. If your program is printing "Alarm Clock" then you haven't set up your $SIG{ALRM} handler correctly. You didn't show us that part of the code. "Alarm Clock" is what is printed by the default handler for SIGALRM.

montest@XXX-test$ ./test 127.0.0.1
I would print to the socket now, if I knew what I was connected to
montest@XXX-test$ ./test 127.0.0.2
Alarm Clock
montest@XXX-test$
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How about setting your alarm more directly, for more accurate debugging -

$SIG{ALRM} = sub { die "DIE DIE DIE!\n" };
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Show us the actual excerpt of your code -- you're asking us to use our imaginations in dreaming up possibilities for what is obviously a subtle problem.

$SIG{ALRM}=\&AlarmHandler;

Well, that looks right as far as it goes. But if your program is printing "Alarm Clock" and then dieing, then you almost certainly are not setting up your alarm handler properly. Perhaps you are doing this too late, undoing it too early, have it in some conditional that you think is being run but isn't, etc. Perhaps some other code is setting up its own alarm handler and overwriting yours. You might want to step through this with the Perl debugger.

        - tye (but my friends call me "Tye")

ChOas

local($SIG{ALRM}) = $timeout ? sub { undef $fh; }
                               : $SIG{ALRM} || 'DEFAULT';
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