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我想使用 NIO 向/从远程机器发送/接收数据。我可以随时发送或接收数据,当我需要发送数据时,我只是发送它而不需要来自远程机器的任何查询,并且远程机器会定期向我发送数据。我不了解 NIO 机制。什么会在 Selector SelectionKey 上生成和读取或写入事件?是否可以在我这边只使用一个 ServerSocketChannel 从远程机器读取数据并写入数据?这就是我所理解的,但我不明白如何触发写作事件......谢谢你的解释。

我已经做了一些编码,我可以读取来自远程机器的数据,但不能写入。我使用选择器,但我不知道如何写入数据。从未写入记录的消息“handle write”,但在wireshark中我可以看到我的数据包。

    public class ServerSelector {

    private static final Logger logger = Logger.getLogger(ServerSelector.class.getName());
    private static final int TIMEOUT = 3000; // Wait timeout (milliseconds)
    private static final int MAXTRIES = 3;
    private final Selector selector;

    public ServerSelector(Controller controller, int... servPorts) throws IOException {
        if (servPorts.length <= 0) {
            throw new IllegalArgumentException("Parameter(s) : <Port>...");
        }
        Handler consolehHandler = new ConsoleHandler();
        consolehHandler.setLevel(Level.INFO);
        logger.addHandler(consolehHandler);

        // Create a selector to multiplex listening sockets and connections
        selector = Selector.open();

        // Create listening socket channel for each port and register selector
        for (int servPort : servPorts) {
            ServerSocketChannel listnChannel = ServerSocketChannel.open();
            listnChannel.socket().bind(new InetSocketAddress(servPort));

            listnChannel.configureBlocking(false); // must be nonblocking to register
            // Register selector with channel.  The returned key is ignored
            listnChannel.register(selector, SelectionKey.OP_ACCEPT);
        }

        // Create a handler that will implement the protocol
        IOProtocol protocol = new IOProtocol();

        int tries = 0;
        // Run forever, processing available I/O operations
        while (tries < MAXTRIES) {
            // Wait for some channel to be ready (or timeout)
            if (selector.select(TIMEOUT) == 0) { // returns # of ready chans
                System.out.println(".");
                tries += 1;
                continue;
            }

            // Get iterator on set of keys with I/O to process
            Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
            while (keyIter.hasNext()) {
                SelectionKey key = keyIter.next(); // Key is a bit mask
                // Server socket channel has pending connection requests?
                if (key.isAcceptable()) {
                    logger.log(Level.INFO, "handle accept");
                    protocol.handleAccept(key, controller);
                }

                // Client socket channel has pending data?
                if (key.isReadable()) {
                    logger.log(Level.INFO, "handle read");
                    protocol.handleRead(key);
                }

                // Client socket channel is available for writing and
                // key is valid (i.e., channel not closed) ?
                if (key.isValid() && key.isWritable()) {
                    logger.log(Level.INFO, "handle write");
                    protocol.handleWrite(key);
                }
                keyIter.remove(); // remove from set of selected keys
                tries = 0;
            }
        }
    }
}

协议

    public class IOProtocol implements Protocol {

    private static final Logger logger = Logger.getLogger(IOProtocol.class.getName());

    IOProtocol() {
        Handler consolehHandler = new ConsoleHandler();
        consolehHandler.setLevel(Level.INFO);
        logger.addHandler(consolehHandler);
    }

    /**
     *
     * @param key
     * @throws IOException
     */
    @Override
    public void handleAccept(SelectionKey key, Controller controller) throws IOException {
        SocketChannel clntChan = ((ServerSocketChannel) key.channel()).accept();
        clntChan.configureBlocking(false); // Must be nonblocking to register
        controller.setCommChannel(clntChan);
        // Register the selector with new channel for read and attach byte buffer
        SelectionKey socketKey = clntChan.register(key.selector(), SelectionKey.OP_READ | SelectionKey.OP_WRITE, controller);
    }

    /**
     * Client socket channel has pending data
     *
     * @param key
     * @throws IOException
     */
    @Override
    public void handleRead(SelectionKey key) throws IOException {
        Controller ctrller = (Controller)key.attachment();
        try {
            ctrller.readData();
        } catch (CommandUnknownException ex) {
            logger.log(Level.SEVERE, null, ex);
        }
        key.interestOps(SelectionKey.OP_READ | SelectionKey.OP_WRITE);
    }

    /**
     * Channel is available for writing, and key is valid (i.e., client channel
     * not closed).
     *
     * @param key
     * @throws IOException
     */
    @Override
    public void handleWrite(SelectionKey key) throws IOException {

        Controller ctrl = (Controller)key.attachment();
        ctrl.writePendingData();
        if (!buf.hasRemaining()) { // Buffer completely written ?
            // Nothing left, so no longer interested in writes
            key.interestOps(SelectionKey.OP_READ);
        }
    buf.compact();
    }
}

控制器

    /**
     * Fill buffer with data.
     * @param msg The data to be sent
     * @throws IOException 
     */
    private void writeData(AbstractMsg msg) throws IOException {
//        
        writeBuffer = ByteBuffer.allocate(msg.getSize() + 4);
        writeBuffer.putInt(msg.getSize());
        msg.writeHeader(writeBuffer);
        msg.writeData(writeBuffer);
        logger.log(Level.INFO, "Write data - message size : {0}", new Object[]{msg.getSize()});
        logger.log(Level.INFO, "Write data - message : {0}", new Object[]{msg});
    }

    /**
     * Write to the SocketChannel
     * @throws IOException 
     */
    public void writePendingData() throws IOException {
        commChannel.write(writeBuffer);
    }
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3 回答 3

1

ServerSocketChannel用于建立连接,但不发送数据。每个连接都需要一个ServerSocketChannel和一个。SocketChannel

读写使用示例SocketChannel

ByteBuffer buf = ByteBuffer.allocate(48);
int bytesRead = socketChannel.read(buf);

您的程序将在第二行休眠,直到数据到来。您需要将此代码置于无限循环中并在后台运行Thread。当数据到来时,你可以从这个线程处理它,然后等待另一个数据到来。

ByteBuffer buf = ByteBuffer.allocate(48);
buf.clear();
buf.put("Hello!".getBytes());

buf.flip();

while(buf.hasRemaining()) {
    channel.write(buf);
}

没有阻塞方法,所以如果你发送小字节缓冲区,你可以从你的 main 调用它Thread

来源

添加: 不要OP_WRITE在新连接上设置密钥。只有OP_READ. 当你想写一些数据时,你需要通知选择器你想发送一些东西并在事件循环中发送它。好的解决方案是制作一个Queue输出消息。然后按照以下步骤操作:

  • 将数据添加到Queue
  • 设置OP_WRITE为频道键
  • while (keyIter.hasNext())循环中,您将拥有writable key,从队列中写入所有数据并删除OP_WRITE密钥。

我很难理解你的代码,但我想你会发现问题所在。此外,如果您只想拥有一个连接,则无需使用Selector. 这很奇怪,你绑定的很少ServerSocketChannels

于 2012-07-03T11:41:10.787 回答
0

我建议您使用阻塞 NIO(这是 SocketChannel 的默认行为)您不需要使用 Selector,但您可以使用一个线程进行读取,而使用另一个线程进行写入。


根据你的例子。

private final ByteBuffer writeBuffer = ByteBuffer.allocateDirect(1024*1024);

private void writeData(AbstractMsg msg) {
    writeBuffer.clear();
    writeBuffer.putInt(0); // set later
    msg.writeHeader(writeBuffer);
    msg.writeData(writeBuffer);
    writeBuffer.putInt(0, writeBuffer.position());

    writeBuffer.flip();
    while(writeBuffer.hasRemaining())
        commChannel.write(writeBuffer);
}
于 2012-07-03T11:29:53.720 回答
0

什么会在 Selector SelectionKey 上生成和读取或写入事件?

OP_READ:套接字接收缓冲区中存在数据或 EOS。

OP_WRITE:套接字发送缓冲区中的空间。

于 2012-07-03T12:56:51.667 回答