  void readDataAvailable(size_t len) noexcept override {
    std::cerr << "readDataAvailable, len " << len << std::endl;

    currentBuffer.length = len;

    if (wcb_) {
      wcb_->setSocket(socket_);
    }

    // Write back the same data.
    socket_->write(wcb_, currentBuffer.buffer, len, writeFlags);

    buffers.push_back(currentBuffer);
    currentBuffer.reset();
    state = STATE_SUCCEEDED;
  }
  void readDataAvailable(size_t len) noexcept override {
    std::cerr << "readDataAvailable, len " << len << std::endl;

    currentBuffer.length = len;

    if (wcb_) {
      wcb_->setSocket(socket_);
    }

     
    socket_->write(wcb_, currentBuffer.buffer, len, writeFlags);

    buffers.push_back(currentBuffer);
    currentBuffer.reset();
    state = STATE_SUCCEEDED;
  }