基于Netty的多人聊天室实现：服务器与客户端详细指南

本指南将引导您使用Netty框架构建一个功能完善的多人聊天室。您将学习如何设置服务器和客户端，处理消息以及实现基本功能，如用户登录、聊天和私信。

一、服务器端

1. 项目依赖

首先，确保您的项目中包含Netty库。您可以从https://netty.io/下载，并将jar文件添加到您的项目依赖中。

2. 服务器代码

以下是使用Netty构建多人聊天服务器的Java代码：javaimport io.netty.bootstrap.ServerBootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;import io.netty.channel.EventLoopGroup;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 io.netty.util.concurrent.DefaultEventExecutorGroup;import io.netty.util.concurrent.EventExecutorGroup;

import java.util.concurrent.ConcurrentHashMap;

public class MultiChatServer { private final int port; private final ConcurrentHashMap<String, ChannelHandlerContext> userMap = new ConcurrentHashMap<>(); private final EventExecutorGroup group = new DefaultEventExecutorGroup(16);

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

public void run() throws Exception {        EventLoopGroup bossGroup = new NioEventLoopGroup();        EventLoopGroup workerGroup = new NioEventLoopGroup();        try {            ServerBootstrap b = new ServerBootstrap();            b.group(bossGroup, workerGroup)                    .channel(NioServerSocketChannel.class)                    .childHandler(new ChannelInitializer<SocketChannel>() {                        @Override                        public void initChannel(SocketChannel ch) throws Exception {                            ch.pipeline().addLast(new StringDecoder(), new StringEncoder(), new MultiChatServerHandler(userMap, group));                        }                    })                    .option(ChannelOption.SO_BACKLOG, 128)                    .childOption(ChannelOption.SO_KEEPALIVE, true);

        ChannelFuture f = b.bind(port).sync();            f.channel().closeFuture().sync();        } finally {            workerGroup.shutdownGracefully();            bossGroup.shutdownGracefully();        }    }

public static void main(String[] args) throws Exception {        int port = 8080;        new MultiChatServer(port).run();    }}

3. `MultiChatServerHandler` 类

该类处理所有传入的消息并执行相应的操作：javaimport io.netty.channel.ChannelFuture;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.SimpleChannelInboundHandler;import io.netty.util.concurrent.EventExecutorGroup;

import java.util.Map;import java.util.concurrent.ConcurrentHashMap;

public class MultiChatServerHandler extends SimpleChannelInboundHandler { private final ConcurrentHashMap<String, ChannelHandlerContext> userMap; private final EventExecutorGroup group;

public MultiChatServerHandler(ConcurrentHashMap<String, ChannelHandlerContext> userMap, EventExecutorGroup group) {        this.userMap = userMap;        this.group = group;    }

@Override    public void channelActive(ChannelHandlerContext ctx) throws Exception {        System.out.println('Client connected: ' + ctx.channel().remoteAddress());    }

@Override    public void channelInactive(ChannelHandlerContext ctx) throws Exception {        System.out.println('Client disconnected: ' + ctx.channel().remoteAddress());        userMap.values().remove(ctx);    }

@Override    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {        String[] tokens = msg.split('\|');        String command = tokens[0];

    switch (command) {            case 'LOGIN':                handleLogin(ctx, tokens[1], tokens[2]);                break;            case 'LIST':                handleList(ctx);                break;            case 'MSG':                handleMessage(ctx, tokens[1], tokens[2]);                break;            case 'PRIVATE':                handlePrivateMessage(ctx, tokens[1], tokens[2]);                break;            default:                ctx.writeAndFlush('Invalid command: ' + command);                break;        }    }

private void handleLogin(ChannelHandlerContext ctx, String username, String password) {        if (userMap.containsKey(username)) {            ctx.writeAndFlush('User already logged in: ' + username);        } else {            userMap.put(username, ctx);            ctx.writeAndFlush('Login successful: ' + username);        }    }

private void handleList(ChannelHandlerContext ctx) {        StringBuilder sb = new StringBuilder();        sb.append('Available chat rooms:

'); for (Map.Entry<String, ChannelHandlerContext> entry : userMap.entrySet()) { sb.append(entry.getKey()).append(' '); } ctx.writeAndFlush(sb.toString()); }

private void handleMessage(ChannelHandlerContext ctx, String roomName, String message) {        StringBuilder sb = new StringBuilder();        sb.append('[').append(ctx.channel().remoteAddress()).append('] ').append(message).append('

'); for (Map.Entry<String, ChannelHandlerContext> entry : userMap.entrySet()) { if (entry.getKey().equals(roomName)) { entry.getValue().writeAndFlush(sb.toString()); } } }

private void handlePrivateMessage(ChannelHandlerContext ctx, String recipient, String message) {        StringBuilder sb = new StringBuilder();        sb.append('[').append(ctx.channel().remoteAddress()).append('] (private) ').append(message).append('

'); if (userMap.containsKey(recipient)) { userMap.get(recipient).writeAndFlush(sb.toString()); } else { ctx.writeAndFlush('User not found: ' + recipient); } }

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

二、客户端

1. 客户端代码

以下是使用Netty构建多人聊天客户端的Java代码：javaimport io.netty.bootstrap.Bootstrap;import io.netty.channel.ChannelFuture;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInitializer;import io.netty.channel.ChannelOption;import io.netty.channel.EventLoopGroup;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.BufferedReader;import java.io.InputStreamReader;

public class MultiChatClient { private final String host; private final int port; private ChannelHandlerContext ctx;

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

public void run() throws Exception {        EventLoopGroup group = new NioEventLoopGroup();        try {            Bootstrap b = new Bootstrap();            b.group(group)                    .channel(NioSocketChannel.class)                    .option(ChannelOption.SO_KEEPALIVE, true)                    .handler(new ChannelInitializer<SocketChannel>() {                        @Override                        public void initChannel(SocketChannel ch) throws Exception {                            ch.pipeline().addLast(new StringDecoder(), new StringEncoder(), new MultiChatClientHandler());                        }                    });

        ChannelFuture f = b.connect(host, port).sync();            ctx = f.channel().pipeline().context(MultiChatClientHandler.class);            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));            while (true) {                String line = in.readLine();                if (line == null) {                    break;                }                ctx.writeAndFlush(line + '

'); } } finally { group.shutdownGracefully(); } }

public static void main(String[] args) throws Exception {        String host = 'localhost';        int port = 8080;        new MultiChatClient(host, port).run();    }}

2. `MultiChatClientHandler` 类

该类处理从服务器接收到的消息：javaimport io.netty.channel.ChannelHandlerContext;import io.netty.channel.SimpleChannelInboundHandler;

public class MultiChatClientHandler extends SimpleChannelInboundHandler { @Override protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception { System.out.println(msg); }

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

三、编译和运行

1. 编译代码并打包成jar文件

在代码根目录下执行以下命令：bashjavac -cp 'path/to/netty-all-4.1.65.Final.jar' *.javajar cvfm MultiChatServer.jar Manifest.txt *.classjar cvfm MultiChatClient.jar Manifest.txt *.class

其中，path/to/netty-all-4.1.65.Final.jar是你下载的Netty库的路径。

2. 运行服务器

在终端中执行以下命令：bashjava -jar MultiChatServer.jar

这将启动一个多人聊天服务器，监听默认端口8080。

3. 运行客户端

在另一个终端中执行以下命令：bashjava -jar MultiChatClient.jar localhost 8080

这将连接到运行在本地主机上的服务器，并启动一个命令行界面，可以在其中输入聊天消息。

总结

本指南介绍了如何使用Netty框架构建一个简单的多人聊天室。您可以根据自己的需求扩展此代码，添加更多功能，例如用户注册、房间管理和文件传输。

基于Netty的多人聊天室实现：服务器与客户端详细指南