### Create the listening socket:
$listen_socket = IO::Socket::INET->
        new('Listen'    => 5,
            'LocalAddr' => $server_host,
            'LocalPort' => $listen_port,
            'Proto'     => "TCP",
            );
# ...

### Handle login attempts:
my $listen_bit = $listen_socket->fileno();
if (vec($r_vec, $listen_bit, 1) == 1)
    {
    print "Login attempt on listening socket...\n";
    my $socket = $listen_socket->accept();
    # ...
    }
# ...

### Handle reading, and possible client dropout:
$bytes_read = $socket->sysread($r_buf, _POSIX_PIPE_BUF, 0);
# ...
elsif ($bytes_read == 0) { do_socket_close_and_cleaup(); }
# ...