/** called when the selector receives a OP_ACCEPT message */
  private void onAccept(@NotNull final SelectionKey key) throws IOException {

    final ServerSocketChannel server = (ServerSocketChannel) key.channel();
    final SocketChannel channel = server.accept();
    channel.configureBlocking(false);
    channel.socket().setReuseAddress(true);
    channel.socket().setTcpNoDelay(true);
    channel.socket().setSoTimeout(0);
    channel.socket().setSoLinger(false, 0);

    final Attached attached = new Attached();
    channel.register(selector, OP_WRITE | OP_READ, attached);

    throttle(channel);

    attached.entryReader = new TcpSocketChannelEntryReader();
    attached.entryWriter = new TcpSocketChannelEntryWriter();

    attached.isServer = true;
    attached.entryWriter.identifierToBuffer(localIdentifier);
  }
  /** called when the selector receives a OP_CONNECT message */
  private void onConnect(@NotNull final SelectionKey key) throws IOException, InterruptedException {

    final SocketChannel channel = (SocketChannel) key.channel();
    final Attached attached = (Attached) key.attachment();

    try {
      if (!channel.finishConnect()) {
        return;
      }
    } catch (SocketException e) {
      quietClose(key, e);
      attached.connector.connect();
      throw e;
    }

    attached.connector.setSuccessfullyConnected();

    if (LOG.isDebugEnabled())
      LOG.debug(
          "successfully connected to {}, local-id={}",
          channel.socket().getInetAddress(),
          localIdentifier);

    channel.configureBlocking(false);
    channel.socket().setTcpNoDelay(true);
    channel.socket().setSoTimeout(0);
    channel.socket().setSoLinger(false, 0);

    attached.entryReader = new TcpSocketChannelEntryReader();
    attached.entryWriter = new TcpSocketChannelEntryWriter();

    key.interestOps(OP_WRITE | OP_READ);

    throttle(channel);

    // register it with the selector and store the ModificationIterator for this key
    attached.entryWriter.identifierToBuffer(localIdentifier);
  }