docs: @Override
      public void settle() throws IllegalStateException {
          lock.lock();
          try {
              checkState(connectionOpen);
              step = InitStep.WAITING_FOR_CHANNEL_CLOSE;
              log.info("Sending a CLOSE message to the server and waiting for response indicating successful settlement.");
              conn.sendToServer(Protos.TwoWayChannelMessage.newBuilder()
                      .setType(Protos.TwoWayChannelMessage.MessageType.CLOSE)
                      .build());
          } finally {
              lock.unlock();
          }
      }