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

my $noBlock = 1;

## Create an array of udp listeners
my @listeners = map{
    my $listener = IO::Socket::INET->new(
        LocalPort => $_,
        Proto => 'udp',
        Reuse => 1,
##        Blocking => 0, ## No apparent effect on Win32.
    ) or die $!, $^E;
    ioctl( $listener, 0x8004667e, \$noBlock ); ## non-blocking on Win32
    $listener;
} 10001 .. 10005;

## forever, but not too fast
while( sleep 1 ) {
    my( $msg, $client );

    ## iterate the listening ports
    for( 0 .. $#listeners ) {

        ## Read anything they have available
        ## Should check if there is more
        $client = $listeners[ $_ ]->recv( $msg, 1024, 0 )
            ## and skip on if nothing there
            or warn "Nothing from $_\n" and next;

        ## Work out who's talking to us
        my( $port, $x ) = sockaddr_in( $client );
        my $ip = inet_ntoa( $x );

        ## And do **WHATEVER** with their message.
        print "$ip:$port : $msg"
    }
}