code: function () {
                  req.date = new Date();
                  if (self._conn.options.customHeaders){
                      var headers = self._conn.options.customHeaders;
                      for (var header in headers) {
                          if (headers.hasOwnProperty(header)) {
                              req.xhr.setRequestHeader(header, headers[header]);
                          }
                      }
                  }
                  req.xhr.send(req.data);
              }
docs: Fires the XHR request -- may be invoked immediately or on a gradually expanding retry window for reconnects