recv in socket programming

madhu.hanigadde has asked for the wisdom of the Perl Monks concerning the following question:

Hi all, am trying to interacting with a server.I should get a response from the server when i will send a command. But there is a chance where i wont get response sometimes. In my code the recv function will get the response wen the server sends, but if there is no response then recv will hangout and will wait till the response come...i want it to wait for sometime and should comeout... Here is my code....

#!/usr/bin/perl
use IO::Socket;
$|=1;
$socket = new IO::Socket::INET (
                                  PeerAddr  => '$IP',
                                  PeerPort  =>  3575,
                                  Proto => 'tcp',
                               )
or die "Couldn't connect to Server\n";

while (1)
{
        $send_data = "CHK $ARGV[0]";
        print STDERR "\nSEND( TYPE q or Q to Quit):$send_data\n";
        if ($send_data ne 'q' and $send_data ne 'Q')
        {
                $socket->send($send_data);
                sleep(1);
                $socket->recv($recv_data1,1024);
                sleep(1);
                $socket->recv($recv_data2,10240);
                print "RECIEVED: $recv_data2\n";
                close $socket;
                last;
        }
        else
        {
            $socket->send($send_data);
            close $socket;
            last;
        }
}
[download]

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Re: recv in socket programming by gone2015 (Deacon) on Feb 12, 2009 at 13:20 UTC
If the far end simply stops responding, but leaves the connection open, then you are indeed in for a long wait. BTW `send` and `recv` are really packet level operations... and may not be what you really want with TCP. In particular, `$socket->recv($recv_data2,10240);` is unlikely to return anything like 10K of data. So you need to implement a time-out. You can use an `ALRM` signal to do this -- but it's a bit messy and won't work on all systems (notably not on Windows -- go figure). So I'd use `IO::Select`, as in the example below. Read more... See the code (4 kB)	[reply] [d/l] [select]
Re: recv in socket programming by irah (Pilgrim) on Feb 12, 2009 at 12:39 UTC
You can use Non-blocking I/O concept. Please use IO::Socket::Inet.	[reply]
Re: recv in socket programming by weismat (Friar) on Feb 12, 2009 at 12:33 UTC
You may use IO::Select before the recv to determine if yoy can read from the socket. Example: `my $select=new IO::Select(); $select->add($socket); if ($select->can_read($timeout)` [download]	[reply] [d/l]