Java NIO：TCP Socket 通信實現

客戶端實現（SocketChannel）

使用 SocketChannel 實現非阻塞 TCP 客戶端：

public class Client {
    public static void main(String[] args) {
        try (SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("localhost", 8088))) {
            socketChannel.configureBlocking(false);
            ByteBuffer byteBuffer = ByteBuffer.allocate(512);
            socketChannel.write(ByteBuffer.wrap("this is client send message".getBytes()));
            while (true) {
                byteBuffer.clear();
                int readBytes = socketChannel.read(byteBuffer);
                if (readBytes > 0) {
                    byteBuffer.flip();
                    System.out.println(new String(byteBuffer.array(), 0, readBytes));
                    socketChannel.close();
                    break;
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

服務端實現（ServerSocketChannel + Selector）

使用 ServerSocketChannel 和 Selector 實現多路復用服務端：

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocketChannel serverChannel = ServerSocketChannel.open();
        serverChannel.socket().bind(new InetSocketAddress(8088));
        serverChannel.configureBlocking(false);
        Selector selector = Selector.open();
        serverChannel.register(selector, SelectionKey.OP_ACCEPT);

        while (true) {
            selector.select();
            Set readyKeys = selector.selectedKeys();
            Iterator iterator = readyKeys.iterator();
            while (iterator.hasNext()) {
                SelectionKey key = iterator.next();
                iterator.remove();
                if (key.isAcceptable()) {
                    System.out.println("accept");
                    ByteBuffer byteBuffer = ByteBuffer.allocate(512);
                    ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
                    SocketChannel socketChannel = ssc.accept();
                    socketChannel.configureBlocking(false);
                    int readKeys = socketChannel.read(byteBuffer);
                    if (readKeys > 0) {
                        byteBuffer.flip();
                        System.out.println(new String(byteBuffer.array(), 0, readKeys));
                    }
                    socketChannel.write(ByteBuffer.wrap("接收到了".getBytes()));
                } else if (key.isReadable()) {
                    System.out.println("read");
                } else if (key.isWritable()) {
                    System.out.println("write");
                }
            }
        }
    }
}