Netty 通过WebSocket编程实现服务器和客户端长连接

思路

利用WebSocketServerProtocolHandler 进行实现 其原理是利用101状态码讲http协议转换为websocket协议

服务端

package com.jhj.netty.websocket;

import com.jhj.netty.heartbeat.MyServerHandler;
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;
import io.netty.handler.timeout.IdleStateHandler;

import java.util.concurrent.TimeUnit;

public class MyServer {
    
    public static void main(String[] args) throws Exception{
    
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try{
    
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
    

                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
    
                            ChannelPipeline pipeline = ch.pipeline();


                            //因为基于Http协议 所以使用http的编码和解码器
                            pipeline.addLast(new HttpServerCodec());
                            //以块方式写添加 ChunkedWrite 处理器
                            pipeline.addLast(new ChunkedWriteHandler());

                            /**
                             * 说明
                             * http数据在传输过程中的分段的，HttpObjectAggregator,就是可以将多个段聚合
                             * 这就是为什么 当浏览器发送大量数据时，就会发出多次http请求
                             */
                            pipeline.addLast(new HttpObjectAggregator(8192));

                            /*
                            说明
                            对应websocket,它的数据是以帧（frame）形式传播
                            可以看到webSocketFrame 下面有六个子类
                            浏览器请求时 ws://localhost:7000/xxx表示请求的uri xxx与下面参数对应
                            WebSocketServerProtocolHandler 核心功能是将http协议升级为ws协议，保持长连接
                            是通过一个状态码 101 讲http转化为websocket 
                             */
                            pipeline.addLast(new WebSocketServerProtocolHandler("/hello"));

                            //自定义的handler 处理业务
                            pipeline.addLast(new MyTextWebSocketFrameHandler());
                        }
                    });

            //启动服务器
            ChannelFuture channelFuture = serverBootstrap.bind(7000).sync();
            channelFuture.channel().closeFuture().sync();



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

服务端Handler

package com.jhj.netty.websocket;

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

import java.time.LocalDate;
import java.time.LocalDateTime;


/**
 * TextWebSocketFrame表示一个文本帧（frame）
 */
public class MyTextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
    

    //当web客户端连接后，触发方法
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
    
        //id表示唯一的值，longtext值是唯一的 shortText 不是唯一的
        System.out.println("handlerAdded 被调用"+ctx.channel().id().asLongText());
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
    
        System.out.println("handlerRemoved 被调用"+ctx.channel().id().asLongText());
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, TextWebSocketFrame msg) throws Exception {
    
        System.out.println("服务器收到消息"+msg.text());

        //回复消息
        ctx.channel().writeAndFlush(new TextWebSocketFrame("服务器时间"+ LocalDateTime.now()+msg.text()));
    }

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

Html页面

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script>
        var socket;
        //判断当前浏览器支不支持 websocket
        if (window.WebSocket){
      
            socket = new WebSocket("ws://localhost:7000/hello");

            //相当于channelReado ev收到服务器端会送的消息
            socket.onmessage=function (ev){
      
                let rt = document.getElementById("responseText");
                rt.value=rt.value+"\n"+ev.data;
            }

            //相当于连接开启
            socket.onopen=function (ev){
      
                let rt = document.getElementById("responseText");
                rt.value="连接开启";
            }

            //相当于连接关闭
            socket.onclose=function (ev){
      
                let rt = document.getElementById("responseText");
                rt.value=rt.value+"\n"+"连接关闭";
            }
        }else{
      
            alert("当前浏览器不支持websocket")
        }

        //发送消息服务器
        function send(message){
      
            if (!window.socket){
      
                //先判断webSocket是否创建好了

                return;
            }

            if (socket.readyState == WebSocket.OPEN){
      
                //open状态
                socket.send(message);
            }else {
      
                alert("连接没有开启")
            }

        }
    </script>
    <form onsubmit="return false">
        <textarea name="message" style="height: 300px;width: 300px"></textarea>
        <input type="button" value="发生消息" onclick="send(this.form.message.value)"></input>
        <textarea id="responseText" style="height: 300px;width: 300px"></textarea>
        <input type="button" value="清空消息" onclick="document.getElementById('responseText').value=''"></input>
    </form>
</body>
</html>

作者声明

如有问题，欢迎指正！