java：网络编程（服务器发送，客户端读取）

public class WriteServer {
    public static void main(String[] args) throws IOException {
        Selector selector = Selector.open();
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);
        ssc.register(selector, SelectionKey.OP_ACCEPT);
        ssc.bind(new InetSocketAddress(8080));
        while (true) {
            selector.select();
            Iterator<SelectionKey> iter = selector.selectedKeys().iterator();
            while (iter.hasNext()) {
                SelectionKey key = iter.next();
                iter.remove();
                if (key.isAcceptable()) {
                    SocketChannel sc = ssc.accept();
                    sc.configureBlocking(false);
                    SelectionKey scKey = sc.register(selector, 0, null);
                    scKey.interestOps(SelectionKey.OP_READ);

                    // 1. 向客户端发送大量数据
                    StringBuilder sb = new StringBuilder();
                    for (int i = 0; i < 5000000; i++) {
                        sb.append("a");
                    }
                    ByteBuffer buffer = Charset.defaultCharset().encode(sb.toString());

                    // 2. 返回值代表实际写入的字节数
                    int writeNums = sc.write(buffer);
                    System.out.println(writeNums);

                    // 3. 判断是否有剩余内容
                    if (buffer.hasRemaining()) {
                        // 4. 关注可写事件
                        scKey.interestOps(scKey.interestOps() + SelectionKey.OP_WRITE);
                        // 5. 把未写完的数据挂到scKey上
                        scKey.attach(buffer);
                    }
                } else if (key.isWritable()) {
                    SocketChannel sc = (SocketChannel) key.channel();
                    ByteBuffer buffer = (ByteBuffer) key.attachment();
                    int write = sc.write(buffer);
                    System.out.println(write);

                    // 6. 清理操作
                    if (!buffer.hasRemaining()) {
                        // 需要清除buffer
                        key.attach(null);
                        // 不再关注可写事件
                        key.interestOps(key.interestOps() - SelectionKey.OP_WRITE);
                    }
                }
            }
        }
    }
}

public class WriteClient {
    public static void main(String[] args) throws IOException {
        SocketChannel sc = SocketChannel.open();
        sc.connect(new InetSocketAddress("localhost", 8080));

        // 客户端接收数据
        int count = 0;
        while (true) {
            ByteBuffer buffer = ByteBuffer.allocate(1024 * 1024);
            count += sc.read(buffer);
            System.out.println(count);
            buffer.clear();
        }
    }
}