netty demo

以下是一个简单的 Netty 服务器和客户端的示例代码：

服务端：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.SimpleChannelInboundHandler;
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 io.netty.util.CharsetUtil;

public class NettyServerDemo {

    private static final int PORT = 8080;

    public static void main(String[] args) {
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(new NioEventLoopGroup(), new NioEventLoopGroup())
                .channel(NioServerSocketChannel.class)
                .childHandler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ChannelPipeline pipeline = ch.pipeline();
                        pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
                        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
                        pipeline.addLast(new SimpleChannelInboundHandler<String>() {
                            @Override
                            protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
                                System.out.println("Server received: " + msg);
                                ctx.writeAndFlush("Hello from server!");
                            }
                        });
                    }
                });
        Channel channel = serverBootstrap.bind(PORT).syncUninterruptibly().channel();
        System.out.println("Server started on port " + PORT);
        channel.closeFuture().addListener((ChannelFutureListener) future -> {
            System.out.println("Server stopped.");
        });
    }
}

客户端：

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.SimpleChannelInboundHandler;
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 io.netty.util.CharsetUtil;

import java.util.Scanner;

public class NettyClientDemo {

    private static final String HOST = "localhost";
    private static final int PORT = 8080;

    public static void main(String[] args) {
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(new NioEventLoopGroup())
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        ChannelPipeline pipeline = ch.pipeline();
                        pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
                        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
                        pipeline.addLast(new SimpleChannelInboundHandler<String>() {
                            @Override
                            protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
                                System.out.println("Client received: " + msg);
                            }
                        });
                    }
                });
        Channel channel = bootstrap.connect(HOST, PORT).syncUninterruptibly().channel();
        System.out.println("Client connected to server on " + HOST + ":" + PORT);
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine();
            if ("exit".equals(line)) {
                break;
            }
            channel.writeAndFlush(line);
        }
        channel.close().addListener((ChannelFutureListener) future -> {
            System.out.println("Client disconnected from server.");
        });
    }
}

这个示例代码实现了一个简单的文本协议，客户端输入的所有内容都会发送到服务端，服务端会将收到的消息原样返回给客户端。你可以基于这个示例代码构建更复杂的网络应用。