netty 实现群聊

　　服务端 Server

package com.oy.groupchat;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class Server {
    private int port;
    public Server(int port) {
        this.port = port;
    }

    public static void main(String[] args) throws Exception {
        new Server(8000).run();
    }

    public void run() throws Exception {
        EventLoopGroup boss = new NioEventLoopGroup(1);
        EventLoopGroup work = new NioEventLoopGroup();

        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap
                    .channel(NioServerSocketChannel.class)
                    .group(boss, work)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    .childHandler(new GroupChatServerChannelInitializer());

            // 绑定端口，启动服务
            ChannelFuture future = bootstrap.bind(port).sync();
            System.out.println("server started and listen " + port);
            // 监听关闭
            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            boss.shutdownGracefully();
            work.shutdownGracefully();
        }
    }
}

　　服务器端 Channel 初始化器 GroupChatServerChannelInitializer

package com.oy.groupchat;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class GroupChatServerChannelInitializer extends ChannelInitializer<SocketChannel> {

    protected void initChannel(SocketChannel socketChannel) throws Exception {
        /* 向管道加入处理器 */
        ChannelPipeline pipeline = socketChannel.pipeline();
        pipeline.addLast("decoder", new StringDecoder()); // 解码器
        pipeline.addLast("encoder", new StringEncoder()); // 编码器
        // 添加自定义的处理器
        pipeline.addLast("GroupChatServerHandler", new GroupChatServerHandler());
    }

}

　　服务器端自定义的 handler---GroupChatServerHandler

package com.oy.groupchat;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;

import java.text.SimpleDateFormat;
import java.util.Date;

public class GroupChatServerHandler extends SimpleChannelInboundHandler<String> {

    // 定义一个 channel 组，管理所有的 channel
    // GlobalEventExecutor.INSTANCE 是全局的事件执行器，单例
    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    /**
     * 一旦连接，第一个执行
     * 将当前 channel 加入到 channelGroup
     */
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        // 将该客户加入聊天的信息推送给其他在线的客户端
        channelGroup.writeAndFlush(sdf.format(new Date()) + " [客户端]" + channel.remoteAddress() + " 加入聊天\n");
        channelGroup.add(channel);
    }

    /**
     * 断开连接
     */
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        // 将该客户离开聊天的信息推送给其他在线的客户端
        channelGroup.writeAndFlush(sdf.format(new Date()) + " [客户端]" + channel.remoteAddress() + " 离开\n");
        System.out.println("当前 channelGroup 大小：" + channelGroup.size());
    }

    /**
     * 表示 channel 处于活动状态， 提示上线
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + "上线了。" + sdf.format(new Date()));
    }

    /**
     * 表示 channel 处于不活动状态， 提示下线
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + "下线了。" + sdf.format(new Date()));
    }

    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        // 获取当前 channel
        final Channel channel = ctx.channel();

        // 遍历 channelGroup，根据不同的情况，返回不同的消息
        channelGroup.forEach(ch -> {
            if (channel != ch) { // 不是当前 channel, 转发消息
                ch.writeAndFlush("[客户端]" + channel.remoteAddress() + "发送了消息：" + msg + "\n");
            } else {
                ch.writeAndFlush("[自己]" + channel.remoteAddress() + "发送了消息：" + msg + "\n");
            }
        });

    }

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

　　客户端 Client

package com.oy.groupchat;

import com.oy.helloworld.NettyClient;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

import java.util.Scanner;

public class Client {
    private static final String HOST = "127.0.0.1";
    private static final int PORT = 8000;

    public static void main(String[] args) {
        new Client().run(HOST, PORT);
    }

    public void run(String host, int port) {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap client = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new GroupChatClientChannelInitializer());
                        }
                    });

            ChannelFuture future = client.connect(host, port).sync();
            System.out.println("--------------" + future.channel().localAddress() + "--------------");

            Channel channel = future.channel();
            // 客户端输入信息
            Scanner scanner = new Scanner(System.in);
            while (scanner.hasNext()) {
                String msg = scanner.nextLine();
                channel.writeAndFlush(msg + "\r\n");
            }

            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
        }
    }
}

　　GroupChatClientChannelInitializer

package com.oy.groupchat;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class GroupChatClientChannelInitializer extends ChannelInitializer<SocketChannel> {

    protected void initChannel(SocketChannel socketChannel) throws Exception {
        /* 向管道加入处理器 */
        ChannelPipeline pipeline = socketChannel.pipeline();
        pipeline.addLast("decoder", new StringDecoder()); // 解码器
        pipeline.addLast("encoder", new StringEncoder()); // 编码器
        // 添加自定义的处理器
        pipeline.addLast("GroupChatClientHandler", new GroupChatClientHandler());
    }

}

　　GroupChatClientHandler

package com.oy.groupchat;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class GroupChatClientHandler extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        System.out.println(msg);
    }
}

　　启动服务端程序和 3 个客户端程序

　　客户端发送消息

---

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