netty传输文件示例代码，包括发送和接收

以下是一个 Netty 传输文件的示例代码，包括发送和接收。这个示例代码使用 Java 语言编写，可以在 Windows、Linux 等各种操作系统上运行。

发送端的代码：

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.io.File;
import java.io.FileInputStream;
import java.util.concurrent.TimeUnit;

public class FileSender {
    private String host;
    private int port;

    public FileSender(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public void sendFile(String filePath) throws Exception {
        final File file = new File(filePath);

        Bootstrap b = new Bootstrap();
        b.group(new NioEventLoopGroup())
                .channel(NioSocketChannel.class)
                .option(ChannelOption.TCP_NODELAY, true)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ch.pipeline().addLast(new StringEncoder(), new StringDecoder(), new FileSenderHandler(file));
                    }
                });

        ChannelFuture future = b.connect(host, port).sync();

        future.channel().closeFuture().sync();
    }

    private class FileSenderHandler extends ChannelInboundHandlerAdapter {
        private File file;
        private FileInputStream fis;

        public FileSenderHandler(File file) {
            this.file = file;
        }

        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            String fileName = file.getName() + "\n";
            String fileSize = String.valueOf(file.length()) + "\n";
            ctx.writeAndFlush(Unpooled.copiedBuffer(fileName.getBytes()));
            ctx.writeAndFlush(Unpooled.copiedBuffer(fileSize.getBytes()));
            fis = new FileInputStream(file);
        }

        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            if (msg instanceof String) {
                String response = (String) msg;
                if ("OK\n".equals(response)) { // 服务端已经准备好接收文件
                    byte[] buf = new byte[1024];
                    int len = 0;
                    while ((len = fis.read(buf)) != -1) {
                        ctx.writeAndFlush(Unpooled.copiedBuffer(buf, 0, len));
                    }
                    TimeUnit.MILLISECONDS.sleep(500); // 等待一段时间确保数据已经被发送完毕
                    ctx.close(); // 发送完毕后关闭 channel
                } else { // 服务端出现错误
                    System.out.println("Server error: " + response);
                    ctx.close();
                }
            }
        }

        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
            fis.close();
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
            cause.printStackTrace();
            ctx.close();
        }
    }

    public static void main(String[] args) throws Exception {
        FileSender sender = new FileSender("127.0.0.1", 9090);
        sender.sendFile("D:/test.zip");
    }
}

接收端的代码：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.io.File;
import java.io.FileOutputStream;

public class FileReceiver {
    private int port;

    public FileReceiver(int port) {
        this.port = port;
    }

    public void start() throws Exception {
        ServerBootstrap b = new ServerBootstrap();
        b.group(new NioEventLoopGroup())
                .channel(NioServerSocketChannel.class)
                .option(ChannelOption.SO_BACKLOG, 1024)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ch.pipeline().addLast(new StringEncoder(), new StringDecoder(), new FileReceiveHandler());
                    }
                });

        ChannelFuture future = b.bind(port).sync();
        System.out.println("FileReceiver started and listening on " + port);

        future.channel().closeFuture().sync();
    }

    private class FileReceiveHandler extends ChannelInboundHandlerAdapter {
        private FileOutputStream fos;
        private String fileName;
        private long fileSize;
        private long receivedSize;

        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            if (msg instanceof String) {
                String response = (String) msg;
                if (fileName == null) {
                    fileName = response.trim();
                    return;
                }
                if (fileSize <= 0) {
                    fileSize = Long.parseLong(response.trim());
                    File file = new File("./" + fileName);
                    fos = new FileOutputStream(file);
                    ctx.writeAndFlush(Unpooled.copiedBuffer("OK\n".getBytes()));
                    return;
                }
            }

            if (fos == null) {
                System.out.println("FileReceiver error: invalid message received");
                return;
            }

            byte[] data = (byte[]) msg;
            fos.write(data); // 写入文件
            receivedSize += data.length;

            if (receivedSize == fileSize) { // 文件接收完成
                fos.close();
                System.out.println("FileReceiver: file " + fileName + " received, size=" + fileSize);
                ctx.close(); // 关闭 channel
            }
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
            cause.printStackTrace();
            ctx.close();
        }
    }

    public static void main(String[] args) throws Exception {
        FileReceiver receiver = new FileReceiver(9090);
        receiver.start();
    }
}

这个示例代码中实现了一个简单的客户端和服务端，可以在两者之间传输文件。通过该示例代码，你可以学习到如何使用 Netty 实现文件传输。