java SocketChannel实现文件传输 服务端用Selector 客户端和服务端怎么写

服务端的代码如下所示：

import java.io.FileOutputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.Iterator;
import java.util.Set;

public class Server {
    private static final int BUFFER_SIZE = 1024;
    private static final String SAVE_DIR = "path/to/save/directory";

    public static void main(String[] args) throws IOException {
        // 创建Selector和ServerSocketChannel
        Selector selector = Selector.open();
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.bind(new InetSocketAddress(8888));
        serverSocketChannel.configureBlocking(false);
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

        System.out.println("Server started...");

        while (true) {
            // 监听事件
            selector.select();

            Set<SelectionKey> selectedKeys = selector.selectedKeys();
            Iterator<SelectionKey> keyIterator = selectedKeys.iterator();

            while (keyIterator.hasNext()) {
                SelectionKey key = keyIterator.next();

                if (key.isAcceptable()) {
                    // 接受客户端连接
                    ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
                    SocketChannel clientChannel = serverChannel.accept();
                    clientChannel.configureBlocking(false);
                    clientChannel.register(selector, SelectionKey.OP_READ);
                    System.out.println("Accepted connection from client: " + clientChannel.getRemoteAddress());
                } else if (key.isReadable()) {
                    // 读取客户端发送的文件
                    SocketChannel channel = (SocketChannel) key.channel();
                    receiveFile(channel);
                    channel.close();
                }

                keyIterator.remove();
            }
        }
    }

    private static void receiveFile(SocketChannel channel) throws IOException {
        // 创建保存文件的目录
        Path saveDir = Path.of(SAVE_DIR);
        if (!Files.exists(saveDir)) {
            Files.createDirectories(saveDir);
        }

        // 创建文件输出流
        String fileName = "received_file.txt";
        Path filePath = saveDir.resolve(fileName);
        FileOutputStream fos = new FileOutputStream(filePath.toFile());

        // 创建缓冲区
        ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);

        int bytesRead;
        while ((bytesRead = channel.read(buffer)) != -1) {
            buffer.flip();
            fos.getChannel().write(buffer);
            buffer.clear();
        }

        fos.close();
        System.out.println("File received: " + filePath);
    }
}

客户端的代码如下所示：

import java.io.FileInputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;

public class Client {
    private static final int BUFFER_SIZE = 1024;
    private static final String FILE_PATH = "path/to/file";

    public static void main(String[] args) throws IOException {
        // 创建Selector和SocketChannel
        Selector selector = Selector.open();
        SocketChannel socketChannel = SocketChannel.open();
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_CONNECT);
        socketChannel.connect(new InetSocketAddress("localhost", 8888));

        while (true) {
            // 监听事件
            selector.select();

            for (SelectionKey key : selector.selectedKeys()) {
                if (key.isConnectable()) {
                    // 完成连接
                    SocketChannel channel = (SocketChannel) key.channel();
                    if (channel.finishConnect()) {
                        channel.register(selector, SelectionKey.OP_WRITE);
                        System.out.println("Connected to server: " + channel.getRemoteAddress());
                    }
                } else if (key.isWritable()) {
                    // 发送文件给服务端
                    SocketChannel channel = (SocketChannel) key.channel();
                    sendFile(channel);
                    channel.close();
                    break;
                }
            }

            selector.selectedKeys().clear();
        }
    }

    private static void sendFile(SocketChannel channel) throws IOException {
        // 创建文件输入流
        FileInputStream fis = new FileInputStream(FILE_PATH);

        // 创建缓冲区
        ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);

        int bytesRead;
        while ((bytesRead = fis.getChannel().read(buffer)) != -1) {
            buffer.flip();
            channel.write(buffer);
            buffer.clear();
        }

        fis.close();
        System.out.println("File sent: " + FILE_PATH);
    }
}

以上代码实现了基于SocketChannel的文件传输，其中服务端使用Selector进行事件监听和处理，客户端连接服务端后发送文件。请注意修改代码中的文件路径和保存目录路径适应你的实际情况。