Netty快速入门(六)

Netty实现服务器和客户端WebSocket长连接

要求：
实现基于WebSocket的长连接的全双工交互
改变http协议多次请求的约束实现长连接，服务器可以发送消息给浏览器
客户端和浏览器端会相互感知对方是否关闭连接

代码

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
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.stream.ChunkedWriteHandler;

public class HttpLongServer {
    public static void main(String[] args) {
        EventLoopGroup boss = new NioEventLoopGroup(1);
        EventLoopGroup work = new NioEventLoopGroup();
        try{
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(boss,work)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG,128)
                    .childOption(ChannelOption.SO_KEEPALIVE,true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            ChannelPipeline pipeline = socketChannel.pipeline();
                            //基于http协议所以需要http协议解码器
                            pipeline.addLast(new HttpServerCodec());
                            //以块的方式读写需要增加chunkedWriteHandler
                            pipeline.addLast(new ChunkedWriteHandler());
                            //http在传输中是分段的需要使用httpObjectAggregator来进行聚合
                            pipeline.addLast(new HttpObjectAggregator(8192));
                            //websocket使用帧形式传递需要使用websocketServerProtoHandler把http请求转为ws请求
                            pipeline.addLast(new WebSocketServerProtocolHandler("/hello"));
                            pipeline.addLast(new MyHttpServerHandler());
                        }
                    });
            ChannelFuture future = serverBootstrap.bind(8899).sync();
            future.channel().closeFuture().sync();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            boss.shutdownGracefully();
            work.shutdownGracefully();
        }
    }
}

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

import java.time.LocalDate;

public class MyHttpServerHandler extends SimpleChannelInboundHandler<TextWebSocketFrame> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, TextWebSocketFrame textWebSocketFrame) throws Exception {
        //输出
        System.out.println("服务器接收到消息:"+textWebSocketFrame.text());
        channelHandlerContext.channel().writeAndFlush(new TextWebSocketFrame("["+LocalDate.now()+"服务器已接收到消息]"+ textWebSocketFrame.text()));
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println("已连接到服务器"+ LocalDate.now());
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        System.out.println("已断开服务器"+ LocalDate.now());
    }

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

前端页面`

<textarea name="message" style="height: 200px;width: 400px"></textarea>
<!-- 这个send的value其实也可以通过值得到-->
<input type="button" value="发送数据" onclick="send(this.form.message.value)">
<textarea id="responseText" style="width: 400px;height: 200px"></textarea>
<input type="button" onclick="document.getElementById('responseText').value=''" value="清空内容">

`

实现效果