http://www.perlmonks.org?node_id=1221484


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