You never had the opportunity to accept any connection from the client side. Add $sock to IO::Select is no good, as it is not an "active channel" yet. Add the accept(), plus fix some minor syntax stuff, your code works.

use strict;
use warnings;

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

my $sock = IO::Socket::INET->new(
                                Proto=>"tcp",
                                LocalHost=>"localhost",
                                Listen=>16,
                                Reuse=>1,
                                LocalPort=>3000
                                ) or die("Could not create socket!\n")
+;

my $connection = $sock->accept();
my $readSet = new IO::Select();
$readSet->add($connection);
while(1) {
    my @rhSet = IO::Select->select($readSet, undef, undef, 0);
    foreach my $rh (@{$rhSet[0]}) {
        my $buf=<$rh>;
        if($buf)
        {
                printf "$buf";
        } else
        {
                $readSet->remove($rh);
                close($rh);
        }
    }
}
[download]

Client side test code:

use IO::Socket;

my $sock = IO::Socket::INET->new(
                                Proto=>"tcp",
                                PeerHost=>"localhost",
                                PeerPort=>3000
                                ) or die("Could not create socket!\n")
+;


print $sock "abcd\n";
[download]

Well, I leave it to you to add back the code to accept further connections.