If one end simply stops sending packets (including closing its end without sending a 'FIN') the other end will wait pretty much indefinitely. (I have tried this with a server running on Linux and Windows XP -- Perl 5.10.0.)

Could tell me how, on XP, you can drop the connection between this server:

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

my $server = new IO::Socket::INET(
    Timeout   => 500,
    Proto     => "tcp",
    LocalPort => 54321,
    Reuse     => 1,
    Listen    => 5
) or die $^E;

my $client = $server->accept;

print while <$client>;

print "client went away";
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and this client:

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

my $con = IO::Socket::INET->new( 'localhost:54321' );

print $con "ping"  while sleep 1;

print "client ended";
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Without the server noticing?