root/tags/1.3/wp-admin/includes/update.php

<?php
/*
// The admin side of our 1.0 update system

function core_update_footer( $msg ) {
    if ( !current_user_can('manage_options') )
        return sprintf( '| '.__( 'Version %s' ), $GLOBALS['wp_version'] );

    $cur = get_option( 'update_core' );

    switch ( $cur->response ) {
    case 'development' :
        return sprintf( '| '.__( 'You are using a development version (%s). Cool! Please <a href="%s">stay updated</a>.' ), $GLOBALS['wp_version'], 'http://wordpress.org/download/svn/' );
    break;

    case 'upgrade' :
        return sprintf( '| <strong>'.__( 'Your WordPress %s is out of date. <a href="%s">Please update</a>.' ).'</strong>', $GLOBALS['wp_version'], $cur->url );
    break;

    case 'latest' :
    default :
        return sprintf( '| '.__( 'Version %s' ), $GLOBALS['wp_version'] );
    break;
    }
}
add_filter( 'update_footer', 'core_update_footer' );

function update_nag() {
    $cur = get_option( 'update_core' );

    if ( ! isset( $cur->response ) || $cur->response != 'upgrade' )
        return false;

    if ( current_user_can('manage_options') )
        $msg = sprintf( __('A new version of WordPress is available! <a href="%s">Please update now</a>.'), $cur->url );
    else
        $msg = __('A new version of WordPress is available! Please notify the site administrator.');

    echo "<div id='update-nag'>$msg</div>";
}
add_action( 'admin_notices', 'update_nag', 3 );

function wp_update_plugins() {
    global $wp_version;

    if ( !function_exists('fsockopen') )
        return false;

    $plugins = get_plugins();
    $active  = get_option( 'active_plugins' );
    $current = get_option( 'update_plugins' );

    $new_option = '';
    $new_option->last_checked = time();

    $plugin_changed = false;
    foreach ( $plugins as $file => $p ) {
        $new_option->checked[ $file ] = $p['Version'];

        if ( !isset( $current->checked[ $file ] ) ) {
            $plugin_changed = true;
            continue;
        }

        if ( $current->checked[ $file ] != $p['Version'] )
            $plugin_changed = true;
    }

    if (
        isset( $current->last_checked ) &&
        43200 > ( time() - $current->last_checked ) &&
        !$plugin_changed
    )
        return false;

    $to_send->plugins = $plugins;
    $to_send->active = $active;
    $send = serialize( $to_send );

    $request = 'plugins=' . urlencode( $send );
    $http_request  = "POST /plugins/update-check/1.0/ HTTP/1.0\r\n";
    $http_request .= "Host: api.wordpress.org\r\n";
    $http_request .= "Content-Type: application/x-www-form-urlencoded; charset=" . get_option('blog_charset') . "\r\n";
    $http_request .= "Content-Length: " . strlen($request) . "\r\n";
    $http_request .= 'User-Agent: WordPress/' . $wp_version . '; ' . get_bloginfo('url') . "\r\n";
    $http_request .= "\r\n";
    $http_request .= $request;

    $response = '';
    if( false != ( $fs = @fsockopen( 'api.wordpress.org', 80, $errno, $errstr, 3) ) && is_resource($fs) ) {
        fwrite($fs, $http_request);

        while ( !feof($fs) )
            $response .= fgets($fs, 1160); // One TCP-IP packet
        fclose($fs);
        $response = explode("\r\n\r\n", $response, 2);
    }

    $response = unserialize( $response[1] );

    if ( $response )
        $new_option->response = $response;

    update_option( 'update_plugins', $new_option );
}
add_action( 'load-plugins.php', 'wp_update_plugins' );

function wp_plugin_update_row( $file ) {
    global $plugin_data;
    $current = get_option( 'update_plugins' );
    if ( !isset( $current->response[ $file ] ) )
        return false;

    $r = $current->response[ $file ];

    echo "<tr><td colspan='5' class='plugin-update'>";
    printf( __('There is a new version of %s available. <a href="%s">Download version %s here</a>.'), $plugin_data['Name'], $r->url, $r->new_version );
    echo "</td></tr>";
}
add_action( 'after_plugin_row', 'wp_plugin_update_row' );
*/
?>