IO::Socket hanging during requests

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

Hi all, hoping someone could cast an eye over this and let me know if you have any thoughts as to whats going on.

In the following piece of code %servers is a hash where the key is an ip address and the value is a port (I don't think it's particularly important to the problem at hand, but the servers are opennap servers).I'm trying to setup connections to these servers using IO::Socket and have been seeing something strange - when the code loops through the %servers hash, every couple of iterations it hangs for a minute or so. Can anyone suggest why this might be happening. The code is as follows:

foreach (keys(%servers)) {
    print "Connecting to $_ :: $servers{$_}: ";

    my $socket;

    $socket = IO::Socket::INET->new(
            PeerAddr => $_,
            PeerPort => $servers{$_},
            Proto    => "tcp",
            Reuse    => 1,
            Type     => SOCK_STREAM);

    if (! defined ($socket)) {
        print "$@\n";
        next;
    }

    print "Connected\n";

    close $socket;
    $socket->DESTROY;
    print "..\n";
}
[download]

When it runs I get something like:

Connecting to 24.164.137.84 :: 3456: IO::Socket::INET: connect: Connec
+tion refused
Connecting to 62.163.22.155 :: 4200: Connected
..                                            (hangs here)
Connecting to 80.117.254.113 :: 8888: IO::Socket::INET: connect: Conne
+ction refused
Connecting to 62.226.24.21 :: 8888: IO::Socket::INET: connect: Connect
+ion refused                   (hangs here)
Connecting to 80.134.24.185 :: 8888: IO::Socket::INET: connect: Connec
+tion refused
Connecting to 217.84.215.47 :: 7777: IO::Socket::INET: connect: Connec
+tion refused
Connecting to 80.133.122.25 :: 7777: IO::Socket::INET: connect: Connec
+tion refused
Connecting to 213.84.39.165 :: 4567: IO::Socket::INET: connect: Connec
+tion refused
Connecting to 24.156.72.65 :: 513: IO::Socket::INET: connect: Connecti
+on refused                     (hangs here)
[download]

But today you took me walking, Through a land that we have lost,
While our children sit at websites, With no access to the cost

Comment on IO::Socket hanging during requests Select or Download Code

Replies are listed 'Best First'.
Re: IO::Socket hanging during requests by fokat (Deacon) on Oct 20, 2002 at 01:29 UTC
TCP involves protocol handshakes when you setup and tear down a connection. In the case where you're connected to the remote server, the delay might be related to the end points (ie, your machine and the remote server) negotiating the closing of the socket. Another possible source for the delay could be the buffering that happens automagically on `STDOUT`. You can get rid of it by saying something like `$\| = 1;` near the beginning of your script. See if this makes the delays go away.	[reply]
Re: IO::Socket hanging during requests by sch (Pilgrim) on Oct 20, 2002 at 05:26 UTC
After playing around some, I think I found out what's going on - the pauses are where there's no server at the other end, so I guess one of three things was happening: We get a connection so we don't get a hang The connection is refused, again we don't get a hang There's no server at the requested address, so it sits waiting for a response, doesn't get one and eventually times out But today you took me walking, Through a land that we have lost, While our children sit at websites, With no access to the cost	[reply]
Re: Re: IO::Socket hanging during requests by Ryszard (Priest) on Oct 20, 2002 at 10:09 UTC
If there is no server at the other end, wont you get a connection refused message? In my client socket code, I always eval the calls to the socket so I can timeout if there is any problems..	[reply]
Re: IO::Socket hanging during requests by sch (Pilgrim) on Oct 20, 2002 at 17:06 UTC
I'm not a 100% certain here, but I thought you only got a connection refused if there was a server at the other end to refuse it. But today you took me walking, Through a land that we have lost, While our children sit at websites, With no access to the cost	[reply]
Re: IO::Socket hanging during requests by sch (Pilgrim) on Oct 20, 2002 at 00:18 UTC
BTW, when I copied and pasted the code section it had tabs - any idea why they've disappeared in the original node? But today you took me walking, Through a land that we have lost, While our children sit at websites, With no access to the cost	[reply]