基于Netty实现WebSocket服务端

本文基于Netty实现WebSocket服务端，实现和客户端的交互通信，客户端基于JavaScript实现。

在【WebSocket简介-CSDN博客】中，我们知道WebSocket是基于Http协议的升级，而Netty提供了Http和WebSocket Frame的编解码器和Handler，我们可以基于Netty快速实现WebSocket服务端。

一、基于Netty快速实现WebSocket服务端

我们可以直接利用Netty提供了Http和WebSocket Frame的编解码器和Handler，快速启动一个WebSocket服务端。服务端收到Client消息后，转发给其他客户端。

服务端代码：

ChannelSupervise：用户存储客户端信息

import io.netty.channel.Channel;
import io.netty.channel.ChannelId;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.util.concurrent.GlobalEventExecutor;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * 用户存储客户端信息
 */
public class ChannelSupervise {
    private static ChannelGroup GlobalGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    private static ConcurrentMap<String, ChannelId> ChannelMap = new ConcurrentHashMap();

    public static void addChannel(Channel channel) {
        GlobalGroup.add(channel);
        ChannelMap.put(channel.id().asShortText(), channel.id());
    }

    public static void removeChannel(Channel channel) {
        GlobalGroup.remove(channel);
        ChannelMap.remove(channel.id().asShortText());
    }

    public static Channel findChannel(String id) {
        return GlobalGroup.find(ChannelMap.get(id));
    }

    public static void send2All(TextWebSocketFrame tws) {
        GlobalGroup.writeAndFlush(tws);
    }
}

服务端Netty配置：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
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.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.stream.ChunkedWriteHandler;

/**
 * 
 * 实现长链接 客户端与服务端；
 */
public class SimpleWsChatServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workGroup).channel(NioServerSocketChannel.class).
            // 在 bossGroup 增加一个日志处理器
                handler(new LoggingHandler(LogLevel.INFO)).childHandler(new ChannelInitializer<SocketChannel>() {

                    @Override
                    protected void initChannel(SocketChannel socketChannel) throws Exception {
                        ChannelPipeline pipeline = socketChannel.pipeline();
                        // 基于http协议的长连接 需要使用http协议的解码 编码器
                        pipeline.addLast(new HttpServerCodec());
                        // 以块的方式处理
                        pipeline.addLast(new ChunkedWriteHandler());
                        /**
                         * http数据传输过程中是分段， HttpObjectAggregator 将多个段聚合起来
                         * 当浏览器发起大量数据的时候，会发起多次http请求
                         */
                        pipeline.addLast(new HttpObjectAggregator(8192));
                        /**
                         * 对于websocket是以frame的形式传递
                         * WebSocketFrame
                         *  浏览器 ws://localhost:7070/ 不在是http协议
                         *  WebSocketServerProtocolHandler 将http协议升级为ws协议 即保持长链接
                         */
                        pipeline.addLast(new WebSocketServerProtocolHandler("/helloWs"));

                        // 自定义handler专门处理浏览器请求
                        pipeline.addLast(new MyTextWebSocketFrameHandler());

                    }
                });
            ChannelFuture channelFuture = serverBootstrap.bind(7070).sync();
            channelFuture.channel().closeFuture().sync();

        } finally {
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }
}

消息转发逻辑：

import com.huawei.websocket.nio2.global.ChannelSupervise;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;

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

/**
 * TextWebSocketFrame  表示一个文本贞
 * 浏览器和服务端以TextWebSocketFrame 格式交互
 */
public class MyTextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd hh:MM:ss");

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, TextWebSocketFrame textWebSocketFrame)
        throws Exception {

        System.out.println("服务端收到消息：" + textWebSocketFrame.text());
        // 回复浏览器

        String resp = sdf.format(new Date()) + ": " + textWebSocketFrame.text();
        // 转发给所有的客户端
        ChannelSupervise.send2All(new TextWebSocketFrame(resp));
        // 发送给当前客户单
        // channelHandlerContext.channel().writeAndFlush(new TextWebSocketFrame(resp));
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        // 添加连接
        System.out.println("客户端加入连接：" + ctx.channel());
        ChannelSupervise.addChannel(ctx.channel());
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        // 断开连接
        System.out.println("客户端断开连接：" + ctx.channel());
        ChannelSupervise.removeChannel(ctx.channel());
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("异常发生：" + cause.getMessage());
        ctx.channel().close();
    }
}

参考：NIO框架Netty+WebSocket实现网页聊天_nio实现websocket-CSDN博客

一、基于Netty，手动处理WebSocket握手信息：

参考：GitCode - 开发者的代码家园https://gitcode.com/Siwash/websocketWithNetty/blob/master/README.md

基于netty搭建websocket，实现消息的主动推送_websocket_rpf_siwash-GitCode 开源社区

服务端代码：

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpServerCodec;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.stream.ChunkedWriteHandler;

import org.apache.log4j.Logger;

/**
 * https://gitcode.com/Siwash/websocketWithNetty/blob/master/README.md
 */
public class NioWebSocketServer {
    private final Logger logger = Logger.getLogger(getClass());

    private void init() {
        logger.info("正在启动websocket服务器");
        NioEventLoopGroup boss = new NioEventLoopGroup();
        NioEventLoopGroup work = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(boss, work);
            bootstrap.channel(NioServerSocketChannel.class);
            bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast("logging", new LoggingHandler("DEBUG"));// 设置log监听器，并且日志级别为debug，方便观察运行流程
                    ch.pipeline().addLast("http-codec", new HttpServerCodec());// 设置解码器
                    ch.pipeline().addLast("aggregator", new HttpObjectAggregator(65536));// 聚合器，使用websocket会用到
                    ch.pipeline().addLast("http-chunked", new ChunkedWriteHandler());// 用于大数据的分区传输
                    ch.pipeline().addLast("handler", new NioWebSocketHandler());// 自定义的业务handler,这里处理WebSocket建链请求和消息发送请求
                }
            });
            Channel channel = bootstrap.bind(7070).sync().channel();
            logger.info("webSocket服务器启动成功：" + channel);
            channel.closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
            logger.info("运行出错：" + e);
        } finally {
            boss.shutdownGracefully();
            work.shutdownGracefully();
            logger.info("websocket服务器已关闭");
        }
    }

    public static void main(String[] args) {
        new NioWebSocketServer().init();
    }
}

import static io.netty.handler.codec.http.HttpUtil.isKeepAlive;

import com.huawei.websocket.nio2.global.ChannelSupervise;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.codec.http.websocketx.CloseWebSocketFrame;
import io.netty.handler.codec.http.websocketx.PingWebSocketFrame;
import io.netty.handler.codec.http.websocketx.PongWebSocketFrame;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshaker;
import io.netty.handler.codec.http.websocketx.WebSocketServerHandshakerFactory;
import io.netty.util.CharsetUtil;

import org.apache.log4j.Logger;

import java.util.Date;

/**
 * 这里处理WebSocket建链请求和消息发送请求
 */
public class NioWebSocketHandler extends SimpleChannelInboundHandler<Object> {

    private final Logger logger = Logger.getLogger(getClass());

    private WebSocketServerHandshaker handshaker;

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
        logger.debug("收到消息：" + msg);
        if (msg instanceof FullHttpRequest) {
            // 以http请求形式接入，但是走的是websocket
            handleHttpRequest(ctx, (FullHttpRequest) msg);
        } else if (msg instanceof WebSocketFrame) {
            // 处理websocket客户端的消息
            handlerWebSocketFrame(ctx, (WebSocketFrame) msg);
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        // 添加连接
        logger.debug("客户端加入连接：" + ctx.channel());
        ChannelSupervise.addChannel(ctx.channel());
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        // 断开连接
        logger.debug("客户端断开连接：" + ctx.channel());
        ChannelSupervise.removeChannel(ctx.channel());
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();
    }

    private void handlerWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) {
        // 判断是否关闭链路的指令
        if (frame instanceof CloseWebSocketFrame) {
            handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());
            return;
        }
        // 判断是否ping消息
        if (frame instanceof PingWebSocketFrame) {
            logger.debug("服务端收到ping消息");
            ctx.channel().write(new PongWebSocketFrame(frame.content().retain()));
            return;
        }

        // 本例程仅支持文本消息，不支持二进制消息
        if (!(frame instanceof TextWebSocketFrame)) {
            logger.debug("本例程仅支持文本消息，不支持二进制消息");
            throw new UnsupportedOperationException(
                String.format("%s frame types not supported", frame.getClass().getName()));
        }
        // 返回应答消息
        String request = ((TextWebSocketFrame) frame).text();
        logger.debug("服务端收到：" + request);
        TextWebSocketFrame tws = new TextWebSocketFrame(new Date().toString() + ctx.channel().id() + "：" + request);
        // 群发
        ChannelSupervise.send2All(tws);
        // 返回【谁发的发给谁】
        // ctx.channel().writeAndFlush(tws);
    }

    /**
     * 唯一的一次http请求，用于创建websocket
     * */
    private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req) {
        // 要求Upgrade为websocket，过滤掉get/Post
        if (!req.decoderResult().isSuccess() || (!"websocket".equals(req.headers().get("Upgrade")))) {
            // 若不是websocket方式，则创建BAD_REQUEST的req，返回给客户端
            sendHttpResponse(ctx, req,
                new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.BAD_REQUEST));
            return;
        }
        logger.debug("服务端收到WebSocket建链消息");
        WebSocketServerHandshakerFactory wsFactory =
            new WebSocketServerHandshakerFactory("ws://localhost:7070/helloWs", null, false);
        handshaker = wsFactory.newHandshaker(req);
        if (handshaker == null) {
            WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
        } else {
            handshaker.handshake(ctx.channel(), req);
        }
    }

    /**
     * 拒绝不合法的请求，并返回错误信息
     * */
    private static void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest req, DefaultFullHttpResponse res) {
        // 返回应答给客户端
        if (res.status().code() != 200) {
            ByteBuf buf = Unpooled.copiedBuffer(res.status().toString(), CharsetUtil.UTF_8);
            res.content().writeBytes(buf);
            buf.release();
        }
        ChannelFuture f = ctx.channel().writeAndFlush(res);
        // 如果是非Keep-Alive，关闭连接
        if (!isKeepAlive(req) || res.status().code() != 200) {
            f.addListener(ChannelFutureListener.CLOSE);
        }
    }
}

这里我们手动处理了握手信息：

可以看到服务端handler日志：

2024-05-24 09:43:51 DEBUG [NioWebSocketHandler] 收到消息：HttpObjectAggregator$AggregatedFullHttpRequest(decodeResult: success, version: HTTP/1.1, content: CompositeByteBuf(ridx: 0, widx: 0, cap: 0, components=0))
GET /helloWs HTTP/1.1
Host: localhost:7070
Connection: Upgrade
Pragma: no-cache
Cache-Control: no-cache
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36 Edg/124.0.0.0
Upgrade: websocket
Origin: null
Sec-WebSocket-Version: 13
Accept-Encoding: gzip, deflate, br, zstd
Accept-Language: zh-CN,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6
Sec-WebSocket-Key: KYh4//SBKLi+nSu6v1kYqw==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
content-length: 0
2024-05-24 09:43:51 DEBUG [NioWebSocketHandler] 服务端收到WebSocket建链消息

Client1的发送和接收消息，在F12小可以看到：

测试用的Client代码如下：

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8">
		<title>
			WebSocket Client
		</title>
	</head>
	<body>
		<script>
			var socket;
			//check current explorer wether support WebSockek
			if (window.WebSocket) {
				socket = new WebSocket("ws://localhost:7070/helloWs");
				//event : msg from server
				socket.onmessage = function(event) {
					console.log("receive msg:" + event.data);
					var rt = document.getElementById("responseText");
					rt.value = rt.value + "\n" + event.data;
				}
				//eq open WebSocket
				socket.onopen = function(event) {
					var rt = document.getElementById("responseText");
					rt.value = "open WebSocket";
				}
				socket.onclose = function(event) {
					var rt = document.getElementById("responseText");
					rt.value = rt.value + "\n" + "close WebSocket";
				}
			
			} else {
				alert("current exploer not support websocket")
			}

			//send msg to WebSocket Server
			function send(message) {
				if (socket.readyState == WebSocket.OPEN) {
					//send msg to WebSocket by socket
					socket.send(message);
				} else {
					alert("WebSocket is not open")
				}
			}
		</script>
		<form onsubmit="return false">
			<textarea name="message" style="height: 300px; width: 300px;"></textarea>
			<input type="button" value="发送消息" onclick="send(this.form.message.value)">
			<textarea id="responseText" style="height: 300px; width: 300px;"></textarea>
			<input type="button" value="清空内容" onclick="document.getElementById('responseText').value=''">
		</form>
	</body>
</html>

直接保存为html文件，使用浏览器打开即可运行测试；