use strict;
use warnings;

use IO::Socket;
use IO::Select;

select( ( select( STDERR ), $| = 1 )[0] );
select( ( select( STDOUT ), $| = 1 )[0] );

my $server = IO::Socket::INET->new( LocalAddr => 'localhost',
                                    Listen => 5,
                                    Proto => 'tcp',
                                    ) or die( "No socket" );
my $port = $server->sockport();

print( STDERR "Created local TCP socket on port $port\n" );

if ( fork() ) {
    print "Parent live\n";

    # wait for connection from just one child
    my $sock = undef;
    sleep( 1 ) while ( ! ( $sock = $server->accept() ) );

    # create select object
    my $rsel = IO::Select->new();
    $rsel->add($sock);

    while (1) {
        my $handles = scalar( $rsel->handles );
        my ( $r ) = IO::Select::select( $rsel, undef, undef, 1 );

        print( STDERR
               "Handles: $handles, "
               . ( $r ? scalar(@{$r}) : "undef" ) . " ready\n" );

        if ( $r && @{$r} )
        {
            foreach ( @{$r} ) {
                print( STDERR "[r]\n" );
                my $buf = "";
                sysread( $_, $buf, 1024 );
                print( STDERR "[d:$buf:d]\n" );
            }
        }
        else
        {
            print( STDERR "[b]\n" );
        }
    }
}
else {
    print "Child live\n";
    close( $server );

    # make internet connection to server
    my $client = IO::Socket::INET->new(
                                       PeerAddr => 'localhost',
                                       PeerPort => $port,
                                       Proto => 'tcp',
                                       )
            or die( "No child connection" );

    while (1) {
        print($client "HELLO!");
        print( STDERR "[W]\n" );
        sleep 3;
    }
}
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