code: function(req, res) {
              return function(err) {
                  err = err || new Error('wsFinalHandler error');
                  err.msg = req.body;
                  var code = json_rpc.ERROR_CODES.methodNotFound;
                  var error = json_rpc.newSysError(req.body, code,
                                                   'Method not found', err);
                  var response = JSON.stringify(json_rpc.reply(error));
                  $._.$.log && $._.$.log.trace(response);
                  res.send(response);
              };
          }
docs: track connections for fast shutdown