Problem with random post

I’ve made a custom page-template to generate random post and re-direct users into that post.

<?php
/**
 * Template Name: Random Post
 */
?>

<?php
    query_posts('orderby=rand');
    while (have_posts()) {
        the_post();
        wp_redirect(get_permalink());
    }
?>

<?php get_header(); ?>
<?php get_footer(); ?>

It works well in localhost, but when I actually applied it on my site. I got this warning while opening the page:

Warning: Cannot modify header information – headers already sent by (output started at /home/admin1/public_html/wp-content/themes/bumi2013/template-random-post.php:7) in /home/admin1/public_html/wp-includes/pluggable.php on line 866

Any idea how to solve this problem?