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asynchronous socket communication with perl tk

by simonz (Sexton)
on Sep 25, 2013 at 12:35 UTC ( #1055676=perlquestion: print w/ replies, xml ) Need Help??
simonz has asked for the wisdom of the Perl Monks concerning the following question:

Hi
I am including a code below which demonstrates a simple client-server communication in a perl tk window. How can I achieve this communication when multiple clients are trying to interact at a time.

server code
use Tk; use IO::Socket; my $status = ''; my $mw = MainWindow->new; $mw->geometry("200x200"); my $buttonFrame = $mw->Frame()->pack(-side => 'bottom'); $buttonFrame->Button(-text => 'Start', -command => sub { init_server(\$mw, \$status) } )->pack(-side => 'left'); my $displayFrame = $mw->Frame()->pack(-side => 'top'); $displayFrame->Label(-text => 'Status:')->pack(-side => 'left'); $displayFrame->Label(-textvariable => \$status)->pack(-side => 'left') +; MainLoop; sub init_server { my ($mw_ref, $status_ref) = @_; my $server = IO::Socket::INET::->new( Proto => 'tcp', LocalPort => 55555, Listen => 1, Reuse => 1 ) or die "Server can't start: $!"; my $client = $server->accept(); $client->autoflush; $$mw_ref->fileevent($client, 'readable', sub { if (defined(my $read = <$client>)) { chomp $read; $$status_ref = $read; } }); }
client code
use IO::Socket; my $client = IO::Socket::INET::->new( Proto => 'tcp', PeerAddr => 'localhost', PeerPort => 55555 ) or die "Client can't connect: $!"; my @msgs = qw(msg1 msg2 msg3 msg4 msg5); for (@msgs) { print $client "$_\n"; sleep 1; }

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Re: asynchronous socket communication with perl tk
by kcott (Abbot) on Sep 25, 2013 at 13:18 UTC

    G'day simonz,

    You took that code from this thread (which has exactly the same name): asynchronous socket comunication with perl tk

    In that thread, the request was for: "... an example of asynchronous socket communication happening through a perl tk application. A very simple and primitive one."

    When I wrote that code last month, I included links to related documentation. If you follow those links, particularly the ones to sections of perlipc, you'll find examples of more complex socket I/O (including multiple clients).

    -- Ken

      Hi, I have made the following modifications in the server code for asynchronous communication, but the server gui hangs as I start the client.

      use strict; use warnings; use Tk; use IO::Socket; use IO::Select; my $status = ''; my $mw = MainWindow->new; $mw->geometry("200x200"); my $buttonFrame = $mw->Frame()->pack(-side => 'bottom'); $buttonFrame->Button(-text => 'Start', -command => sub { init_server(\$mw, \$status) } )->pack(-side => 'left'); my $displayFrame = $mw->Frame()->pack(-side => 'top'); $displayFrame->Label(-text => 'Status:')->pack(-side => 'left'); $displayFrame->Label(-textvariable => \$status)->pack(-side => 'left') +; my $server; MainLoop; sub init_server { my ($mw_ref, $status_ref) = @_; $server = IO::Socket::INET::->new( Proto => 'tcp', LocalPort => 55555, Listen => 1, Reuse => 1 ) or die "Server can't start: $!"; =cut my $client = $server->accept(); $client->autoflush; $$mw_ref->fileevent($client, 'readable', sub { if (defined(my $read = <$client>)) { chomp $read; $$status_ref = $read; } }); =cut #my $client = $server->accept(); $$mw_ref->fileevent($server, 'readable', sub { my $readable_handles = new IO::Select(); $readable_handles->add($server); my $buf; while (1) { #Infinite loop # select() blocks until a socket is ready to be read or written my ($new_readable) = IO::Select->select($readable_handles, undef, undef, 0); print "Inside while \n"; # If it comes here, there is at least one handle # to read from or write to. For the moment, worry only about # the read side. foreach my $sock (@$new_readable) { print "Inside foreach $sock \n"; if ($sock == $server) { my $new_sock = $sock->accept(); # Add it to the list, and go back to select because the # new socket may not be readable yet. $readable_handles->add($new_sock); } else { # It is an ordinary client socket, ready for reading. $buf = <$sock>; if ($buf) { # .... Do stuff with $buf $$status_ref = $buf; } else { # Client closed socket. We do the same here, and remov +e # it from the readable_handles list $readable_handles->remove($sock); close($sock); } } } } } ); }

      Hi
      I even modified the server code to make it working, i removed the gui portion. Now when i am starting the server and then starting the client from another terminal , it works. However, the first time when I start client.pl, it prints msg1, then stops. Again when i start client.pl , it prints msg1 amd msg2. Similarly third time msg1, msg2,msg3 .

      My question is

      1. why not all the five messages msg1..msg5 are getting printed in one go when i start client.pl

      The client code remains as it is as posted before
      Can someone please explain me the flow of the code.

      my $server; $server = IO::Socket::INET::->new( Proto => 'tcp', LocalPort => 55555, Listen => 1, Reuse => 1 ) or die "Server can't start: $!"; my $readable_handles = new IO::Select(); my $buf; while (my $client = $server->accept) { #Infinite loop # select() blocks until a socket is ready to be read or written my ($new_readable) = IO::Select->select($readable_handles, undef, undef, 0); # print "Inside while \n"; # If it comes here, there is at least one handle # to read from or write to. For the moment, worry only about # the read side. $readable_handles->add($client); foreach my $sock (@$new_readable) { if ($sock == $server) { my $new_sock = $sock->accept(); # Add it to the list, and go back to select because the # new socket may not be readable yet. $readable_handles->add($new_sock); } else { # It is an ordinary client socket, ready for reading. $buf = <$sock>; if ($buf) { # .... Do stuff with $buf #$$status_ref = $buf; print $buf ; } else { # Client closed socket. We do the same here, and remov +e # it from the readable_handles list $readable_handles->remove($sock); #close($sock); } } } }

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