index.php

<?php
/**
 * The main template file
 *
 * This is the most generic template file in a WordPress theme
 * and one of the two required files for a theme (the other being style.css).
 * It is used to display a page when nothing more specific matches a query.
 * E.g., it puts together the home page when no home.php file exists.
 *
 * @link https://developer.wordpress.org/themes/basics/template-hierarchy/
 *
 */

get_header();

?>
<?php

if( ! ( function_exists( 'wp_get_attachment_by_post_name' ) ) ) {
    function wp_get_attachment_by_post_name( $post_name ) {
            $args           = array(
                'posts_per_page' => 1,
                'post_type'      => 'attachment',
                'name'           => trim( $post_name ),
            );

            $get_attachment = new WP_Query( $args );

            if ( ! $get_attachment || ! isset( $get_attachment->posts, $get_attachment->posts[0] ) ) {
                return false;
            }

            return $get_attachment->posts[0];
    }
}
?>
<code>index.php</code>
<?php
echo $_SERVER['SERVER_ADDR'];
?>
<?php the_content() ?>
<?php
get_footer();