docs: private void error(ErrorReason error)
      {
          if (options.rawSocket) {
              //  For raw sockets, send a final 0-length message to the application
              //  so that it knows the peer has been disconnected.
              Msg terminator = new Msg();
              processMsg.apply(terminator);
          }
          assert (session != null);
          socket.eventDisconnected(endpoint, fd);
          session.flush();
          session.engineError(error);
          unplug();
          destroy();
      }