Unexpected TCP/IP disconnect

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

Hi,

This problem applies to any manner of TCP/IP data exchange, and in this case I'm using POE.

So, using POE::Component::Client::TCP, I'm trying to get some 32 bytes of data from a process. It goes like this. I send a command code, the other guy gets it, and then replies with 32 bytes of data. That's all on the localhost interface. So far so good. Ethereal shows what's going on and the 32 bytes of data are indeed replied. But then, the other guy, after sending his 32-byte reply, *immediately* disconnects, resulting in my POE::Component::Client::TCP exiting with:

Client 2 got read error 0 (Normal disconnection)
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The ServerInput event never gets the data. So I tried getting the data using ServerError and ServerFlushed but it these also do not get the 32 bytes of data before the component exits. If only I could get the data then I could send it to another session to get it process.

Maybe I just got the whole thing not right... Maybe I should use a server component to try to get the data from this other process ?

How would you handle such a TCP/IP process that, once you query it for data, sends it and immediately disconnects.

Any suggestions appreciated !

Comment on Unexpected TCP/IP disconnect Download Code

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Re: Unexpected TCP/IP disconnect
by PodMaster (Abbot) on Feb 21, 2006 at 10:26 UTC

update

Maybe I just got the whole thing not right... Maybe I should use a server component to try to get the data from this other process ?

Maybe you can show some code that demonstrates the problem.

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Re: Unexpected TCP/IP disconnect
by BrowserUk (Patriarch) on Feb 21, 2006 at 12:22 UTC

How would you handle such a TCP/IP process that, once you query it for data, sends it and immediately disconnects.

With threads :)

Using this multithreaded server as a stand in for your 'send 32 bytes and shutdown the connection' server:

#! perl -slw
use strict;
use threads;
use IO::Socket::INET;

my $s = IO::Socket::INET->new( LocalPort => 9999, Listen => 255, reuse
+=>1 );
while( my $c = $s->accept ){
    threads->create( sub {
        printf "Server$$: Got %s", scalar <$c>;
        print $c chr( 65 + rand(26) ) x 32;
        $c->shutdown(2);
    } )->join;
}
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And this client that starts 5 threads that each make five requests to the server, whilst the main thread retrieves the output and 'processes it':

#! perl -slw
use strict;
use threads;
use Thread::Queue;

sub getIt {
    require IO::Socket::INET;
    my $tid = threads->self->tid;
    my( $Q ) = @_;
    my $data;
    for( 1 .. 5 ) {
        my $c = IO::Socket::INET->new( 'localhost:9999' ); ## Connect
        print $c 'Give me 32 bytes please';                ## Ask
        chomp( $data = <$c> );                             ## get
        $c->close;                                         ## close
        $Q->enqueue( "$tid:$data" );                       ## Queue
        sleep int rand( 5 );
     }
     $Q->enqueue( undef );  ## Signal thread done
}

my $Q = new Thread::Queue;
my @threads = map{ threads->create( \&getIt, $Q ) } 1 .. 5;

for( 1 .. 5 ) {                           ## Handle 5 threads dying
    while( my $in = $Q->dequeue() ) {                     ## Get data
        my( $tid, $data ) = split ':', $in; ## Separate who from what
        print "Client: Got '$data' from thread:$tid";
    }
}

$_->join for @threads; ## Wait for threads to die
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A test run looks like this

[12:20:32.79] C:\test>start /b tserver

[12:20:35.60] C:\test>tclient
Server: Got Give me 32 bytes please
Client: Got 'JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ' from thread:4
Server: Got Give me 32 bytes please
Client: Got 'VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV' from thread:1
Server: Got Give me 32 bytes please
Client: Got 'EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE' from thread:3
Server: Got Give me 32 bytes please
Server: Got Give me 32 bytes please
Client: Got 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' from thread:2
Client: Got 'YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY' from thread:5
Server: Got Give me 32 bytes please
Client: Got 'WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW' from thread:4
Server: Got Give me 32 bytes please
Client: Got 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' from thread:4
Server: Got Give me 32 bytes please
Client: Got 'LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL' from thread:4
Server: Got Give me 32 bytes please
Client: Got 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' from thread:5
Server: Got Give me 32 bytes please
Client: Got 'CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC' from thread:2
Server: Got Give me 32 bytes please
Client: Got 'PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP' from thread:4
Server: Got Give me 32 bytes please
Client: Got 'BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB' from thread:1
Server: Got Give me 32 bytes please
Client: Got 'JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ' from thread:3
Server: Got Give me 32 bytes please
Client: Got 'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF' from thread:1
Server: Got Give me 32 bytes please
Client: Got 'HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH' from thread:5
Server: Got Give me 32 bytes please
Client: Got 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' from thread:2
Server: Got Give me 32 bytes please
Client: Got 'DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD' from thread:1
Server: Got Give me 32 bytes please
Client: Got 'WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW' from thread:3
Server: Got Give me 32 bytes please
Client: Got 'BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB' from thread:2
Server: Got Give me 32 bytes please
Client: Got 'WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW' from thread:5
Server: Got Give me 32 bytes please
Client: Got 'NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN' from thread:3
Server: Got Give me 32 bytes please
Client: Got 'IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII' from thread:1
Server: Got Give me 32 bytes please
Client: Got 'UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU' from thread:3
Server: Got Give me 32 bytes please
Client: Got 'TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT' from thread:2
Server: Got Give me 32 bytes please
Client: Got 'RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR' from thread:5
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