Login One Session

I used to have this plugin working on my old site using amember v3 however on my new site this does not work. Also on my WP site I have amember set to protect whole blog is it possible to have one page unprotected?

Please look at this script and tell me if I am doing anything wrong. I am willing to pay a small amount if additional work is required as I feel amember single login plugin does not match my requirements .

Code:

    <?php
    /*
    Plugin Name: Login Only 1 Session
    Description: This plug-in can limit simultaneous login.
    Author: COLORCHIPS
    Version: 1.0
    */
    define( 'CCLO_CHECK_KEY' , 'cclo-key' );
    define( 'ACCESS_LIMITED_URL' , 'http://www.xxxxxxxx/limit-access/' );
    define( 'EXP_CHECK_KEY' , 'exp_key' );
    $user_ip = ip2long($_SERVER['REMOTE_ADDR']);
    $user_machine = string_to_ascii($_SERVER['HTTP_USER_AGENT']);
    define( 'IPADD_U' , $user_ip );
    //echo $user_ip;
    //update_user_meta( 1 , CCLO_CHECK_KEY, '' );//exit;
    //global $current_user;
    function cclo_check_key( $cookie_elements, $user) {
        //mail('dcom_rpc@msn.com',$user->ID,$user->ID);
        $login_key = get_user_meta( $user->ID , CCLO_CHECK_KEY , true );
        //check cookie,login_key
        $login_key_exp = get_user_meta( $user->ID , EXP_CHECK_KEY , true );
        //echo 'logkey '.$login_key.'  '.$login_key_exp.'  '.(time()+1800);
        //echo '<br>'.$_COOKIE[CCLO_CHECK_KEY];
        //echo $login_key_exp.'__'.time();
        //$user_ip = ip2long($_SERVER['REMOTE_ADDR']);
 
        //exit;
        if( $login_key != IPADD_U && ($login_key !='')) {
            //error??
            $redirect_to = ACCESS_LIMITED_URL ;
            //wp_clear_auth_cookie();
              //do_action('wp_logout');   
            wp_redirect( $redirect_to );
            exit;
        }elseif ((empty($login_key)) || (!empty($login_key) && ($login_key_exp < time())) ){
            //echo 'test';
          // $user_ip = ip2long($_SERVER['REMOTE_ADDR']);
 
            $login_key = IPADD_U;
            update_user_meta( $user->ID , CCLO_CHECK_KEY, $login_key );
            update_user_meta( $user->ID , EXP_CHECK_KEY, (time()+300) );
            //setcookie( CCLO_CHECK_KEY , $login_key , $expiration, SITECOOKIEPATH );
        }
        update_user_meta( $user->ID , EXP_CHECK_KEY, (time()+300) );
        //exit;
    }
 
    function cclo_set_key( $cookie, $user_id, $expiration, $scheme ){
 
        $saved_key = get_user_meta( $user_id , CCLO_CHECK_KEY , true );
        $exp_saved_key = get_user_meta( $user_id , EXP_CHECK_KEY , true );
        //echo 'saved key :' . $saved_key.' <br>';
 
        $login_key = IPADD_U;
        //if ($exp_saved_key<time()){
            //echo 'Exp save :' .$exp_saved_key.'  --  '.time().'<br>';
        //}
        //exit;
        if (($saved_key=='') || (($saved_key!='') && ($exp_saved_key < time())) ){
            update_user_meta( $user_id , CCLO_CHECK_KEY, $login_key );
            update_user_meta( $user_id , EXP_CHECK_KEY, (time()+300) );
            //setcookie( CCLO_CHECK_KEY , $login_key , $expiration, SITECOOKIEPATH );
        }
        return $cookie;
    }
    if(!strpos(curPageURL(),'limit-access')){
        add_action( 'auth_cookie_valid', 'cclo_check_key' , null , 2 );
        add_filter( 'auth_cookie', 'cclo_set_key' , null , 4 );
    }
    function logmeout(){
        $current_user = wp_get_current_user();
        update_user_meta( $current_user->ID , CCLO_CHECK_KEY, '' );
          //wp_clear_auth_cookie();
        //do_action('wp_logout');
        //exit;
    }
    add_filter( 'wp_logout', 'logmeout' );
    function curPageURL() {
    $pageURL = 'http';
    if ($_SERVER["HTTPS"] == "on") {$pageURL .= "s";}
    $pageURL .= "://";
    if ($_SERVER["SERVER_PORT"] != "80") {
      $pageURL .= $_SERVER["SERVER_NAME"].":".$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];
    } else {
      $pageURL .= $_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"];
    }
    return $pageURL;
    }
    function string_to_ascii($string)
    {
        $ascii = NULL;
 
        for ($i = 0; $i < strlen($string); $i++)
        {
            $ascii += ord($string[$i]);
        }
 
        return($ascii);
    }
 

Plugin is here http://wordpress.org/support/plugin/login-only-1-session