使用netty实现WebSocket协议通信

服务器与浏览器之间实现通信，一般都是由浏览器发起http请求，服务端对http请求进行响应，要实现服务端主动向浏览器推送数据，一般采用的方案都是websocket主动推送，或者前端实现轮询方式拉取数据，轮询方式多少有点浪费资源，并且消息推送也不够及时。目前很多系统都是采用websocket协议进行主动推送数据给前端。在springboot中是支持websocket协议的，但是这里想讲的是通过netty实现websocket通信。
首先需要引入netty的依赖包

<dependency><groupId>io.netty</groupId><artifactId>netty-all</artifactId><version>4.1.90.Final</version>
</dependency>

这里面已经包含了websocket协议相关的编解码。下面介绍两种方案使用websocket协议，一种是内置的处理ws消息，另外一种是自己实现相关消息的解析和处理。
首先介绍第一种使用，这种方案只需要用户自己定义一个handler实现消息的接收和业务处理，把处理结果返回给浏览器就可以了，大致代码逻辑如下：

1. 定义handler用于处理ws消息：

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;/*** 用户自定义websocket消息处理handler** @Author xingo* @Date 2023/11/21*/
public class UserWebsocketInHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame frame) throws Exception {String text = frame.text();System.out.println(Thread.currentThread().getName() + "|" + text);ctx.writeAndFlush(new TextWebSocketFrame("server send message : " + text));}
}

2. 服务端引入websocket相关handler和自定义handler

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
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.LoggingHandler;
import io.netty.handler.stream.ChunkedWriteHandler;
import io.netty.handler.timeout.IdleStateEvent;
import io.netty.handler.timeout.IdleStateHandler;import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;/*** websocket服务端** @Author xingo* @Date 2023/11/21*/
public class NettyWebsocketServer implements Runnable {/*** 服务端IP地址*/private String ip;/*** 服务端端口号*/private int port;public NettyWebsocketServer(String ip, int port) {this.ip = ip;this.port = port;}@Overridepublic void run() {// 指定boss线程数：主要负责接收连接请求，一般设置为1就可以final EventLoopGroup boss = new NioEventLoopGroup(1, new ThreadFactory() {private AtomicInteger index = new AtomicInteger(0);@Overridepublic Thread newThread(Runnable r) {return new Thread(r, String.format("NioBoss_%d", this.index.incrementAndGet()));}});// 指定worker线程数：主要负责处理连接就绪的连接，一般设置为CPU的核心数final int totalThread = 12;final EventLoopGroup worker = new NioEventLoopGroup(totalThread, new ThreadFactory() {private AtomicInteger index = new AtomicInteger(0);@Overridepublic Thread newThread(Runnable r) {return new Thread(r, String.format("NioSelector_%d_%d", totalThread, this.index.incrementAndGet()));}});// 指定任务处理线程数：主要负责读取数据和处理响应，一般该值设置的比较大，与业务相对应final int jobThreads = 1024;final EventLoopGroup job = new DefaultEventLoopGroup(jobThreads, new ThreadFactory() {private AtomicInteger index = new AtomicInteger(0);@Overridepublic Thread newThread(Runnable r) {return new Thread(r, String.format("NioJob_%d_%d", jobThreads, this.index.incrementAndGet()));}});// 日志处理handler：类定义上面有Sharable表示线程安全，可以将对象定义在外面使用final LoggingHandler LOGGING_HANDLER = new LoggingHandler();// 指定服务端bootstrapServerBootstrap server = new ServerBootstrap();server.group(boss, worker)// 指定通道类型.channel(NioServerSocketChannel.class)// 指定全连接队列大小：windows下默认是200，linux/mac下默认是128.option(ChannelOption.SO_BACKLOG, 2048)// 维持链接的活跃，清除死链接.childOption(ChannelOption.SO_KEEPALIVE, true)// 关闭延迟发送.childOption(ChannelOption.TCP_NODELAY, true)// 添加handler处理链.childHandler(new ChannelInitializer<NioSocketChannel>() {@Overrideprotected void initChannel(NioSocketChannel channel) throws Exception {ChannelPipeline pipeline = channel.pipeline();// 日志处理pipeline.addLast(LOGGING_HANDLER);// 心跳检测：读超时时间、写超时时间、全部超时时间（单位是秒，0表示不处理）pipeline.addLast(new IdleStateHandler(30,0,0, TimeUnit.SECONDS));pipeline.addLast(new ChannelDuplexHandler() {@Overridepublic void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {IdleStateEvent event = (IdleStateEvent) evt;System.out.println("心跳事件 : " + event.state());super.userEventTriggered(ctx, evt);}});// 处理http请求的编解码器pipeline.addLast(job, "httpServerCodec", new HttpServerCodec());pipeline.addLast(job, "chunkedWriteHandler", new ChunkedWriteHandler());pipeline.addLast(job, "httpObjectAggregator", new HttpObjectAggregator(65536));// 处理websocket的编解码器pipeline.addLast(job, "webSocketServerProtocolHandler", new WebSocketServerProtocolHandler("/", "WebSocket", true, 655360));// 自定义处理器pipeline.addLast(job, "userInHandler", new UserWebsocketInHandler());}});try {// 服务端绑定对外服务地址ChannelFuture future = server.bind(ip, port).sync();System.out.println("netty server start ok.");// 等待服务关闭，关闭后释放相关资源future.channel().closeFuture().sync();} catch (InterruptedException e) {e.printStackTrace();} finally {boss.shutdownGracefully();worker.shutdownGracefully();job.shutdownGracefully();}}public static void main(String[] args) {new Thread(new NettyWebsocketServer("127.0.0.1", 8899)).start();}
}

以上就实现了websocket服务端，客户端连接到服务端实现双向通信。
另外一种实现方式是自己定义一个handler用于ws协议数据的解析和处理，这样协议的整个处理过程对于用户来说很清楚明白，下面是实现的逻辑代码：

1. 首先定义一个handler用于ws协议解析和处理：

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.*;
import io.netty.handler.codec.http.websocketx.*;
import io.netty.util.AttributeKey;
import io.netty.util.CharsetUtil;
import lombok.extern.slf4j.Slf4j;/***** @Author xingo* @Date 2023/11/21*/
@Slf4j
public class WebsocketServerHandler extends SimpleChannelInboundHandler<Object> {private WebSocketServerHandshaker handshaker;public WebsocketServerHandler() {}private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame msg) {if (msg instanceof CloseWebSocketFrame) {handshaker.close(ctx.channel(), (CloseWebSocketFrame) msg.retain());return;}if (msg instanceof PingWebSocketFrame) {log.info("websocket ping message");ctx.channel().write(new PingWebSocketFrame(msg.content().retain()));} else if (msg instanceof TextWebSocketFrame) {// websocket消息解压成字符串让下一个handler处理String text = ((TextWebSocketFrame) msg).text();log.info("请求数据|{}", text);// 如果不调用这个方法后面的handler就获取不到数据ctx.fireChannelRead(text);} else {log.error("不支持的消息格式");throw new UnsupportedOperationException("不支持的消息格式");}}private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest msg) {if (!msg.decoderResult().isSuccess()|| (!"websocket".equalsIgnoreCase(msg.headers().get(HttpHeaderNames.UPGRADE)))) {sendHttpResponse(ctx, msg, new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.BAD_REQUEST));return;}WebSocketServerHandshakerFactory wsShakerFactory = new WebSocketServerHandshakerFactory("ws://" + msg.headers().get(HttpHeaderNames.HOST), null, false);handshaker = wsShakerFactory.newHandshaker(msg);if (handshaker == null) {WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());} else {// 建立websocket连接握手handshaker.handshake(ctx.channel(), msg);ctx.channel().attr(AttributeKey.valueOf("add")).set(Boolean.TRUE);}}private void sendHttpResponse(ChannelHandlerContext ctx, FullHttpRequest msg, DefaultFullHttpResponse response) {if (response.status().code() != HttpResponseStatus.OK.code()) {ByteBuf buf = Unpooled.copiedBuffer(response.status().toString(), CharsetUtil.UTF_8);response.content().writeBytes(buf);buf.release();}ChannelFuture cf = ctx.channel().writeAndFlush(response);if (!HttpUtil.isKeepAlive(msg) || response.status().code() != HttpResponseStatus.OK.code()) {cf.addListener(ChannelFutureListener.CLOSE);}}@Overridepublic void channelReadComplete(ChannelHandlerContext ctx) throws Exception {ctx.flush();}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {ctx.channel().attr(AttributeKey.valueOf("add")).set(Boolean.FALSE);ctx.close();}@Overridepublic void channelInactive(ChannelHandlerContext ctx) throws Exception {ctx.channel().attr(AttributeKey.valueOf("add")).set(Boolean.FALSE);ctx.close();}@Overrideprotected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {if (msg instanceof FullHttpRequest) {handleHttpRequest(ctx, (FullHttpRequest) msg);} else if (msg instanceof WebSocketFrame) {handleWebSocketFrame(ctx, (WebSocketFrame) msg);}}
}

上面对ws协议进行了处理，处理后的数据直接解析成字符串给后续的handler。

2. 定义两个handler用于数据处理和封装：

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;/*** 入站处理器：获取请求数据，完成业务处理，推送消息给浏览器* * @Author xingo* @Date 2023/11/21*/
public class UserWebsocketInHandler extends SimpleChannelInboundHandler<String> {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {System.out.println(Thread.currentThread().getName() + "|" + msg);//        ctx.writeAndFlush(new TextWebSocketFrame("server send message : " + msg));ctx.writeAndFlush("server send message : " + msg);}
}

import io.netty.channel.*;
import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;/*** 出站处理器：判断数据是否需要进行封装* * @Author xingo* @Date 2023/11/21*/
public class UserWebsocketOutHandler extends ChannelOutboundHandlerAdapter {@Overridepublic void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {if(msg instanceof String) {ctx.write(new TextWebSocketFrame((String) msg), promise);} else {super.write(ctx, msg, promise);}}
}

3. websocket服务端代码

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
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 io.netty.handler.timeout.IdleStateEvent;
import io.netty.handler.timeout.IdleStateHandler;import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;/*** websocket服务端** @Author xingo* @Date 2023/11/21*/
public class NettyWebsocketServer implements Runnable {/*** 服务端IP地址*/private String ip;/*** 服务端端口号*/private int port;public NettyWebsocketServer(String ip, int port) {this.ip = ip;this.port = port;}@Overridepublic void run() {// 指定boss线程数：主要负责接收连接请求，一般设置为1就可以final EventLoopGroup boss = new NioEventLoopGroup(1, new ThreadFactory() {private AtomicInteger index = new AtomicInteger(0);@Overridepublic Thread newThread(Runnable r) {return new Thread(r, String.format("NioBoss_%d", this.index.incrementAndGet()));}});// 指定worker线程数：主要负责处理连接就绪的连接，一般设置为CPU的核心数final int totalThread = 12;final EventLoopGroup worker = new NioEventLoopGroup(totalThread, new ThreadFactory() {private AtomicInteger index = new AtomicInteger(0);@Overridepublic Thread newThread(Runnable r) {return new Thread(r, String.format("NioSelector_%d_%d", totalThread, this.index.incrementAndGet()));}});// 指定任务处理线程数：主要负责读取数据和处理响应，一般该值设置的比较大，与业务相对应final int jobThreads = 1024;final EventLoopGroup job = new DefaultEventLoopGroup(jobThreads, new ThreadFactory() {private AtomicInteger index = new AtomicInteger(0);@Overridepublic Thread newThread(Runnable r) {return new Thread(r, String.format("NioJob_%d_%d", jobThreads, this.index.incrementAndGet()));}});// 日志处理handler：类定义上面有Sharable表示线程安全，可以将对象定义在外面使用final LoggingHandler LOGGING_HANDLER = new LoggingHandler();// 指定服务端bootstrapServerBootstrap server = new ServerBootstrap();server.group(boss, worker)// 指定通道类型.channel(NioServerSocketChannel.class)// 指定全连接队列大小：windows下默认是200，linux/mac下默认是128.option(ChannelOption.SO_BACKLOG, 2048)// 维持链接的活跃，清除死链接.childOption(ChannelOption.SO_KEEPALIVE, true)// 关闭延迟发送.childOption(ChannelOption.TCP_NODELAY, true)// 添加handler处理链.childHandler(new ChannelInitializer<NioSocketChannel>() {@Overrideprotected void initChannel(NioSocketChannel channel) throws Exception {ChannelPipeline pipeline = channel.pipeline();// 日志处理pipeline.addLast(LOGGING_HANDLER);// 心跳检测：读超时时间、写超时时间、全部超时时间（单位是秒，0表示不处理）pipeline.addLast(new IdleStateHandler(30,0,0, TimeUnit.SECONDS));pipeline.addLast(new ChannelDuplexHandler() {@Overridepublic void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {IdleStateEvent event = (IdleStateEvent) evt;System.out.println("心跳事件 : " + event.state());super.userEventTriggered(ctx, evt);}});// 处理http请求的编解码器pipeline.addLast(job, "httpServerCodec", new HttpServerCodec());pipeline.addLast(job, "chunkedWriteHandler", new ChunkedWriteHandler());pipeline.addLast(job, "httpObjectAggregator", new HttpObjectAggregator(65536));// 处理websocket的编解码器pipeline.addLast(job, "websocketHandler", new WebsocketServerHandler());// 自定义处理器pipeline.addLast(job, "userOutHandler", new UserWebsocketOutHandler());pipeline.addLast(job, "userInHandler", new UserWebsocketInHandler());}});try {// 服务端绑定对外服务地址ChannelFuture future = server.bind(ip, port).sync();System.out.println("netty server start ok.");// 等待服务关闭，关闭后释放相关资源future.channel().closeFuture().sync();} catch (InterruptedException e) {e.printStackTrace();} finally {boss.shutdownGracefully();worker.shutdownGracefully();job.shutdownGracefully();}}public static void main(String[] args) {new Thread(new NettyWebsocketServer("127.0.0.1", 8899)).start();}
}

上面这种方式同样实现了websocket通信，并且可以清楚的知道连接创建和数据交互的整个过程。