Whether it's a limitation of Win32 sockets or Perl or sockets in general, attempting to send to a socket whilst simultaneously in attempting to read from it doesn't work. It's not a limitation of threads, though without threads simultaneously reading and writing is a bit harder :)

To alleviate the problem, it's necessary to set the socket into non-blocking mode and use sysread rather than the buffered IO primitives.

This code does pretty much what you've ask for, but don't take it as being a good example of anything :) Just a starting point:

#! perl -slw
use strict;
package threads::SimpleServer;
use threads;
use Thread::Queue;
use IO::Socket qw(:DEFAULT :crlf);
use Time::HiRes qw( usleep );

our @ISA = 'Thread::Queue';

our $die:shared = 0;

sub listener {
    my( $in, $out, $port ) = @_;
    my $sock = new IO::Socket::INET (
        LocalAddr => "localhost", LocalPort => $port,
        Proto => 'tcp', Listen => 1, Reuse => 1
    );

    my $client = $sock->accept;
    async {
        ioctl( $client, 0x8004667e, pack( 'V', 1 ) ) or die $^E;

        my( $buffer, $p ) = ( '', 0 );
        while( not $die ) {
            local $\ = CRLF;
            print $client $out->dequeue while $out->pending;
            my $bytes = sysread( $client, $buffer, 1024, length( $buff
+er ) );
            last unless defined $bytes or 0+$^E == 10035;
            sleep 1 and next unless $p = 1+index( $buffer, CRLF );
            $in->enqueue( substr( $buffer, 0, $p+1, '' ) ) 
                 while $p = 1+index( $buffer, CRLF );
        }
    }->detach;
}

sub new {
    my( $class, %args ) = @_;
    my( $in, $out ) = map{ bless Thread::Queue->new(), $class } 1 .. 2
+;
    threads->create( \&listener, $in, $out, $args{ port } || 1000 )->d
+etach;
    return $in, $out;
}


1;
package main;
use threads;
#use threads::SimpleServer;

my( $in, $out ) = threads::SimpleServer->new( port => 1000 );

async{
    my $reportNo;
    $out->enqueue( 'report:' . ++$reportNo ) while sleep 1;
}->detach;

while( my $cmd = $in->dequeue ) {
    warn "got:'$cmd'";
    $out->enqueue( ( rand > 0.5 ) ? 'OK' : '?' );
}

END{ our $die = 1; sleep 1 }
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