this.mqReq = function( cb, id, l_m, etag ){ // l_m - last modified date
  var self = this;
  if( typeof token == 'undefined' ){
    throw new Error('Not authorized');
  }
  var headers = {};
  if( typeof l_m !== 'undefined'){
    headers['If-Modified-Since'] = l_m;
  } else {
    headers['If-Modified-Since'] = (new Date()).toUTCString();
  }
  if( typeof etag !== 'undefined'){
    headers['If-None-Match'] = etag;
  }
  this._mq = _requestFunction( url + '/mq/req' , 'GET', headers , {id : id}, function( xhr ){
    // Restart itself, except when aborted (status == 0)
    if (xhr.status) {
      if (xhr.status == 200) {
        timeout = 0;
      } else {
        timeout += 1000;
      }
      setTimeout(function(){
        return self.mqReq( cb, id, xhr.getResponseHeader('Last-Modified'), xhr.getResponseHeader('Etag') );
      }, timeout);
    }
    cb( xhr );
  });
  return this._mq;
};