jQuery(document).ready(function() {
    // don't wait 5 sec the first time just make the call
    do_request();

    // periodically call the whoson service
    var periodic_request = setInterval (do_request, 5000 );

    function do_request() {
        jQuery.ajax({
            url : domain_root + '/simsite/php/whoson.php',
            type : 'get',
            dataType : 'json',
            success : function(json) {
                var whoson_container = jQuery('div#whoson');

                whoson_container.replaceWith(json.content);
                if(json.status != 'timeout') {
                    // if the whoson server didn't time out stop requesting periodical by clearing the interval
                    clearInterval (periodic_request);
                }
            }
        });
    }
});