Java NIO 远程传输零拷贝

服务端

public class Server {
    //backlog为accept队列大小，默认值为50
    private static final int BACKLOG = 1024;
    private static final String IP = "127.0.0.1";
    private static final int PORT = 8888;
    private ServerSocketChannel serverChannel;
    private Selector selector;

    //构造函数
    public Server() {
        try {
            //打开服务端通道
            serverChannel = ServerSocketChannel.open();
            //设置非阻塞
            serverChannel.configureBlocking(false);
            //绑定端口，在服务端监听
            serverChannel.bind(new InetSocketAddress(IP, PORT), BACKLOG);
            //打开选择器
            selector = Selector.open();
            //把服务端通道注册到选择器，关注的事件是接收
            serverChannel.register(selector, SelectionKey.OP_ACCEPT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //监听客户端
    public void listen() {
        try {
            //循环等待客户端连接
            for (; ; ) {
                int readChannel = selector.select();
                if (readChannel > 0) {
                    //关注事件集合
                    Set<SelectionKey> selectionKeys = selector.selectedKeys();
                    Iterator<SelectionKey> iterator = selectionKeys.iterator();
                    while (iterator.hasNext()) {
                        SelectionKey key = iterator.next();
                        //如果是OP_ACCEPT，有新的客户端连接
                        if (key.isAcceptable()) {
                            SocketChannel channel = serverChannel.accept();
                            channel.configureBlocking(false);
                            //把通道注册到选择器，关注的事件是读
                            channel.register(selector, SelectionKey.OP_READ);
                            System.out.println(channel.getRemoteAddress() + "已连接，准备传输...");
                        }
                        if (key.isReadable()) {
                            readClient(key);
                        }
                        //移除Selection，因为多线程，要防止重复操作
                        iterator.remove();
                    }
                } else {
                    System.out.println("没有可用通道！");
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //读取客户端
    private void readClient(SelectionKey key) {
        SocketChannel channel = null;
        try {
            channel = (SocketChannel) key.channel();
            //获取buffer
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            //把通道数据放入缓冲区
            int count = channel.read(buffer);
            if (count > 0) {
                //反转读写模式
                buffer.flip();
                //创建fileChannel，把文件放入通道
                FileChannel fileChannel = new FileOutputStream("d:\\test\\write888.txt").getChannel();
                //把Buffer内容放入fileChannel
                fileChannel.write(buffer);
                //fileChannel.transferFrom(channel, 0, 1024);
            }
        } catch (IOException e) {
            try {
                System.out.println(channel.getRemoteAddress() + "断线了...");
                //取消注册
                key.cancel();
                //关闭通道
                channel.close();
            } catch (IOException ioException) {
                ioException.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws Exception {
        Server server = new Server();
        server.listen();
    }
}

客户端

public class Client {
    private static final String IP = "127.0.0.1";
    private static final int PORT = 8888;
    private SocketChannel channel;
    private Selector selector;
    private String user;

    //构造函数
    public Client() throws IOException {
        //打开服务端通道
        channel = SocketChannel.open(new InetSocketAddress(IP, PORT));
        //设置非阻塞
        channel.configureBlocking(false);
        //打开选择器
        selector = Selector.open();
        //把通道注册到选择器，关注的事件是读
        channel.register(selector, SelectionKey.OP_READ);
        user = channel.getLocalAddress().toString();
        System.out.println(user + "已连接...");
    }

    //向服务器发送消息
    private void sendServer() throws IOException {
        //拿到文件
        File file = new File("d:\\test\\write.txt");
        FileInputStream inputStream = new FileInputStream(file);
        //创建管道，把文件放入通道
        FileChannel fileChannel = inputStream.getChannel();
        long transferCount = fileChannel.transferTo(0, fileChannel.size(), channel);
        System.out.println("发送字节数" + transferCount);
        //fileChannel.close();
    }

    public static void main(String[] args) throws Exception {
        Client client = new Client();
        client.sendServer();
    }
}