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Re: Socket hang. (Windows or Perl? Solutions?) (Updated)

by marioroy (Priest)
on Sep 01, 2018 at 02:24 UTC ( #1221484=note: print w/replies, xml ) Need Help??


in reply to Socket hang. (Windows or Perl? Solutions?) (Updated)

Hi BrowserUk,

Today, I came across this thread and like to share the solution used inside MCE::Util to have sockets close immediately on the Windows platform. Below are the relevant lines in the demonstration that follows.

# anything windows, including Cygwin my $is_winenv = ( $^O =~ /mswin|mingw|msys|cygwin/i ); # write a char before calling shutdown syswrite($client, '0') if $is_winenv; $client->shutdown( 2 ); close $client; syswrite($svr, '0') if $is_winenv; $svr->shutdown( 2 ); close $svr;

I ran your demonstration with the fix using Strawberry Perl.

#! perl -slw use strict; use Time::HiRes qw[ time usleep ]; use threads; use threads::shared; use IO::Socket; our $port //= 12345; my $svrN :shared = 0; my $clientN :shared = 0; my $is_winenv = ( $^O =~ /mswin|mingw|msys|cygwin/i ); my $start = time; async { my $svr = IO::Socket::INET->new( Listen => SOMAXCONN, Reuse =>1, LocalPort => $port, Timeout => 0.1, ) or die $!; while( my $client = $svr->accept ) { my $in = <$client>; print $client "echod:$in"; syswrite($client, '0') if $is_winenv; $client->shutdown( 2 ); close $client; ++$svrN; } }->detach; async { while( 1 ) { my $svr = IO::Socket::INET->new( PeerHost => 'localhost', PeerPort => $port, Reuse => 1, Timeout => 0.1, ) or usleep( 10_000 ), next; sleep 0; print $svr ++$clientN; my $echo = <$svr>; sleep 0; syswrite($svr, '0') if $is_winenv; $svr->shutdown( 2 ); close $svr; sleep 0; } }->detach; $|++; while( usleep 100_000 ) { printf "\rserver:$svrN client:$clientN cycles: %.3f/sec", $svrN / ( time() - $start ); }

I pressed Ctrl-C after reaching 200k connections.

Y:\>perl demo_thr.pl server:208500 client:208501 cycles: 2128.246/secTerminating on signal +SIGINT(2)

Running netstat using Cygwin shows no extra connections lingering around. Netstat reports 22 ~ 24 (not more) while Strawberry Perl ran.

$ netstat -na | wc -l 21

Without the fix, netstat reports a high number that keeps increasing due to sockets not closing immediately.

$ netstat -na | wc -l 14055

Regards, Mario

Replies are listed 'Best First'.
Re^2: Socket hang. (Windows or Perl? Solutions?) (Updated)
by marioroy (Priest) on Sep 01, 2018 at 04:25 UTC

    Hi again! BrowserUk's demo is possible for Perl lacking threads support. A condition variable is needed to prevent a race condition, especially for processes that spawn quickly. For example, the 2nd worker attempting to connect before the 1st worker initiates the connection.

    #! perl -slw # Parallel example for Perl not built with threads support. # Based on https://www.perlmonks.org/?node_id=897591. use strict; use Time::HiRes qw[ time usleep ]; use MCE::Hobo; use MCE::Shared; use IO::Socket; our $port //= 12345; my $condvar = MCE::Shared->condvar; my $svrN = MCE::Shared->scalar( 0 ); my $clientN = MCE::Shared->scalar( 0 ); my $is_winenv = ( $^O =~ /mswin|mingw|msys|cygwin/i ); my $start = time; mce_async { my $svr = IO::Socket::INET->new( Listen => SOMAXCONN, Reuse =>1, LocalPort => $port, Timeout => 0.1, ) or die $!; # signal the client ready $condvar->signal; while( my $client = $svr->accept ) { my $in = <$client>; print $client "echod:$in"; syswrite($client, '0') if $is_winenv; $client->shutdown( 2 ); close $client; $svrN->incr; } }; mce_async { # wait for the server connection $condvar->wait; while( 1 ) { my $svr = IO::Socket::INET->new( PeerHost => 'localhost', PeerPort => $port, Reuse => 1, Timeout => 0.1, ) or usleep( 10_000 ), next; sleep 0; print $svr $clientN->incr; my $echo = <$svr>; sleep 0; syswrite($svr, '0') if $is_winenv; $svr->shutdown( 2 ); close $svr; sleep 0; } }; $|++; while( usleep 100_000 ) { my ( $n1, $n2 ) = ( $svrN->get, $clientN->get ); printf "\rserver:$n1 client:$n2 cycles: %.3f/sec", $n1 / ( time() - $start ); }

    Note: MCE::Shared involves sockets. So it will not run as fast as threads::shared. Not to worry, it's not far behind.

    Strawberry Perl

    Y:\>perl demo_thr.pl server:29889 client:29889 cycles: 2119.429/secTerminating on signal SI +GINT(2) Y:\>perl demo_mce.pl server:35619 client:35620 cycles: 1771.711/secTerminating on signal SI +GINT(2)

    Cygwin

    $ perl demo_thr.pl server:31879 client:31879 cycles: 2128.663/sec $ perl demo_mce.pl server:31690 client:31691 cycles: 1856.834/sec

    Regards, Mario

Re^2: Socket hang. (Windows or Perl? Solutions?) (Updated)
by BrowserUk (Pope) on Sep 01, 2018 at 07:50 UTC

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