import org.apache.zookeeper.ClientCnxn.EndOfStreamException; //导入依赖的package包/类
@Override
void doTransport(int waitTimeOut,
                 List<Packet> pendingQueue,
                 ClientCnxn cnxn)
        throws IOException, InterruptedException {
    try {
        if (!firstConnect.await(waitTimeOut, TimeUnit.MILLISECONDS)) {
            return;
        }
        Packet head = null;
        if (needSasl.get()) {
            if (!waitSasl.tryAcquire(waitTimeOut, TimeUnit.MILLISECONDS)) {
                return;
            }
        } else {
            if ((head = outgoingQueue.poll(waitTimeOut, TimeUnit.MILLISECONDS)) == null) {
                return;
            }
        }
        // check if being waken up on closing.
        if (!sendThread.getZkState().isAlive()) {
            // adding back the patck to notify of failure in conLossPacket().
            addBack(head);
            return;
        }
        // channel disconnection happened
        if (disconnected.get()) {
            addBack(head);
            throw new EndOfStreamException("channel for sessionid 0x"
                    + Long.toHexString(sessionId)
                    + " is lost");
        }
        if (head != null) {
            doWrite(pendingQueue, head, cnxn);
        }
    } finally {
        updateNow();
    }
}
 

import org.apache.zookeeper.ClientCnxn.EndOfStreamException; //导入依赖的package包/类
/**
 * @return true if a packet was received
 * @throws InterruptedException
 * @throws IOException
 */
boolean doIO(List<Packet> pendingQueue, LinkedList<Packet> outgoingQueue) throws InterruptedException, IOException {
    boolean packetReceived = false;
    SocketChannel sock = (SocketChannel) sockKey.channel();
    if (sock == null) {
        throw new IOException("Socket is null!");
    }
    if (sockKey.isReadable()) {
        int rc = sock.read(incomingBuffer);
        if (rc < 0) {
            throw new EndOfStreamException(
                    "Unable to read additional data from server sessionid 0x"
                            + Long.toHexString(sessionId)
                            + ", likely server has closed socket");
        }
        if (!incomingBuffer.hasRemaining()) {
            incomingBuffer.flip();
            if (incomingBuffer == lenBuffer) {
                recvCount++;
                readLength();
            } else if (!initialized) {
                readConnectResult();
                enableRead();
                if (!outgoingQueue.isEmpty()) {
                    enableWrite();
                }
                lenBuffer.clear();
                incomingBuffer = lenBuffer;
                packetReceived = true;
                initialized = true;
            } else {
                sendThread.readResponse(incomingBuffer);
                lenBuffer.clear();
                incomingBuffer = lenBuffer;
                packetReceived = true;
            }
        }
    }
    if (sockKey.isWritable()) {
        synchronized (outgoingQueue) {
            if (!outgoingQueue.isEmpty()) {
                ByteBuffer pbb = outgoingQueue.getFirst().bb;
                sock.write(pbb);
                if (!pbb.hasRemaining()) {
                    sentCount++;
                    Packet p = outgoingQueue.removeFirst();
                    if (p.requestHeader != null
                            && p.requestHeader.getType() != OpCode.ping
                            && p.requestHeader.getType() != OpCode.auth) {
                        pendingQueue.add(p);
                    }
                }
            }
        }
    }
    if (outgoingQueue.isEmpty()) {
        disableWrite();
    } else {
        enableWrite();
    }
    return packetReceived;
}