009-核心技术-netty-通过WebSocket编程实现服务器和客户端长连接

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mob604756ebc436 2021-08-09 23:27:00 ©著作权

009-核心技术-netty-通过WebSocket编程实现服务器和客户端长连接
https://blog.51cto.com/u_15127537/4898148

009-核心技术-netty-通过WebSocket编程实现服务器和客户端长连接

一、长连接

http协议是无状态的，浏览器和服务器间的请求相应一次，下一次会重新创建连接

1、服务端代码

package com.github.bjlhx15.netty.demo.netty.websocket;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
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;

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

        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))//在bossGroup增加一个日志处理器
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            //基于http协议 使用http编解码
                            pipeline.addLast(new HttpServerCodec());
//                            是以块方式写，添加ChunkedWriteHandler处理器
                            pipeline.addLast(new ChunkedWriteHandler());
                            // http数据是分段的，HttpObjectAggregator 是将多个端聚合
                            pipeline.addLast(new HttpObjectAggregator(8192));
                            // 对于websocket，数据是以帧（frame）形式传递
                            // WebSocketFrame下有六个子类
                            // 浏览器请求时：ws://localhost:7000/hello 表示请求的URI
                            // WebSocketServerProtocolHandler 核心时将http协议升级为ws协议，保持长连接
                            // 是通过状态码 101切换的，请求地址要匹配
                            pipeline.addLast(new WebSocketServerProtocolHandler("/hello"));
                            pipeline.addLast(new MyTextWebSocketFrameHandler());
                        }
                    });
            ChannelFuture channelFuture = serverBootstrap.bind(7000).sync();

            System.out.println("Server start listen at " + 7000);
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

服务端handler

package com.github.bjlhx15.netty.demo.netty.websocket;

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

import java.time.LocalDateTime;

//TextWebSocketFrame表示一个文本帧
public class MyTextWebSocketFrameHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, TextWebSocketFrame textWebSocketFrame) throws Exception {
        System.out.println("服务端收到消息：" + textWebSocketFrame.text());
        //回复
        channelHandlerContext.channel().writeAndFlush(new TextWebSocketFrame("服务器事件："
                + LocalDateTime.now() + " " + textWebSocketFrame.text()));
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        //id 表示唯一至，asLongText是唯一的，asShortText不是唯一的
        System.out.println("handlerAdded被调用：" + ctx.channel().id().asLongText());
        System.out.println("handlerAdded被调用：" + ctx.channel().id().asShortText());
    }

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

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {

        System.out.println("handlerRemoved 被调用：" + cause.getMessage());
        ctx.close();
    }
}

客户端页面

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<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>
<script>
    var socket;
    if (window.WebSocket) {
        socket = new WebSocket("ws://localhost:7000/hello");
        socket.onmessage = function (ev) {
            let rt = document.getElementById("responseText");
            rt.value = rt.value + "\n" + ev.data;
        }
        socket.onopen = function (ev) {
            let rt = document.getElementById("responseText");
            rt.value = "连接开启";
        }
        socket.onclose = function (ev) {
            let rt = document.getElementById("responseText");
            rt.value = rt.value + "\n" + "连接关闭";
        }
    } else {
        alert("浏览器不支持");
    }

    function send(msg) {
        if (!window.socket) {
            return;
        }
        if (socket.readyState == WebSocket.OPEN) {
            socket.send(msg);
        } else {
            alert("连接没有开启")
        }

    }
</script>
</html>