三、Netty服务器与多客户连接利用广播方式完全理解netty的读写机制

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         本篇采用的编解码是netty自带的字符串的格式的编解码，用户1可以控制台发消息（输入完消息要加换行符号，是一个消息结束的分隔符，后面我会在编解码中详细讲解）给服务器，服务器广播给其他所有的客户端，这个机制，我们游戏开发服务器中应用很普遍，游戏中的广播，游戏中你看到其他玩家在操作。。。都是利用这个广播机制。

案例如下：

package com.zhurong.netty.test3;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

/**
 * Description:
 * User: zhurong
 * Date: 2018-09-24  23:17
 */
public class NettyChatServer {

    public static void main(String[] args) {
        //接收连接
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        //连接发送给work
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            System.out.println("服务器启动成功！");
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).
                    childHandler(new NettyChatServerInitializer());
            ChannelFuture channelFuture = serverBootstrap.bind(8000).sync();
            channelFuture.channel().closeFuture().sync();

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }

}

package com.zhurong.netty.test3;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.Delimiters;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;

/**
 * Description: 客户端与服务器端连接一旦创建，这个类中方法就会被回调
 * User: zhurong
 * Date: 2018-09-24  21:29
 */
public class NettyChatServerInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        //解码器
        pipeline.addLast(new DelimiterBasedFrameDecoder(4096, Delimiters.lineDelimiter()));
        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
        pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
        pipeline.addLast(new NettyChatServerHandler());
    }
}

package com.zhurong.netty.test3;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;

/**
 * 此处定义客户端和服务器端传递的是字符串所以用了String
 * Description:
 * User: zhurong
 * Date: 2018-09-24  23:30
 */
public class NettyChatServerHandler extends SimpleChannelInboundHandler<String> {

    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress()+"------>"+msg);
          //返回数据给客户端,是一个异步的操作
        channelGroup.forEach(channel ->{
            System.out.println("channel:"+channel);
            if(ctx.channel() != channel){
                channel.writeAndFlush(ctx.channel().remoteAddress()+"发送的消息" + msg+"\n");
                System.out.println("发送消息给客户端："+ctx.channel().remoteAddress()+",msg:"+msg+"\n");
            }else {
                channel.writeAndFlush("是自己的消息\n");
                System.out.println("是自己的消息："+ msg);
            }
        });
//        channelGroup.writeAndFlush("服务器已经收到你们客户端消息了！");
    }

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

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println("server 推送的消息："+ ctx.channel().remoteAddress() + "注册进了服务器\n");
        channelGroup.writeAndFlush("server 推送的消息："+ ctx.channel().remoteAddress() + "注册进了服务器\n");
        channelGroup.add(ctx.channel());
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        channelGroup.writeAndFlush("server 推送的消息："+ ctx.channel().remoteAddress() + "离开了服务器\n");
        System.out.println("server 推送的消息："+ ctx.channel().remoteAddress() + "离开了服务器\n");
    }


    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        channelGroup.writeAndFlush(ctx.channel().remoteAddress() + "上线了\n");
        System.out.println(ctx.channel().remoteAddress() + "上线了\n");
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        channelGroup.writeAndFlush(ctx.channel().remoteAddress() + "下线了\n");
        System.out.println(ctx.channel().remoteAddress() + "下线了\n");
    }
}

package com.zhurong.netty.test3;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Description:
 * User: zhurong
 * Date: 2018-09-24  23:37
 */
public class NettyChatClient {

    public static void main(String[] args) throws InterruptedException, IOException {
        EventLoopGroup eventExecutors = new NioEventLoopGroup();
        try {
            System.out.println("客户端启动成功");
            Bootstrap bootstrap =  new Bootstrap();
            bootstrap.group(eventExecutors).channel(NioSocketChannel.class).handler(new NettyChatClientInitializer());
            ChannelFuture channelFuture = bootstrap.connect("localhost",8000).sync();
            Channel channel = channelFuture.channel();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
            for(;;){
                channel.writeAndFlush(bufferedReader.readLine() + "\r\n");
            }
//            channelFuture.channel().closeFuture().sync();

        }finally {
            eventExecutors.shutdownGracefully();
        }

    }
}

package com.zhurong.netty.test3;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.Delimiters;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LengthFieldPrepender;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.util.CharsetUtil;

/**
 *  Netstat –ano|findstr
 * Description: 客户端与服务器端连接一旦创建，这个类中方法就会被回调
 * User: zhurong
 * Date: 2018-09-24  21:29
 */
public class NettyChatClientInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        //解码器
        pipeline.addLast(new DelimiterBasedFrameDecoder(4096, Delimiters.lineDelimiter()));
        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
        pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
        pipeline.addLast(new NettyChatClientHandler());
    }
}

package com.zhurong.netty.test3;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

/**
 * Description:
 * User: zhurong
 * Date: 2018-09-24  22:01
 */
public class NettyChatClientHandler extends SimpleChannelInboundHandler<String> {


    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println("收到服务器的消息："+ctx.channel().remoteAddress() + msg);
//        System.out.println("msg:"+ msg);
//        ctx.writeAndFlush("from client "+ System.currentTimeMillis());
    }

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

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush("acitve客户端第一条信息");
    }
}

现在是不是对netty又进步一熟悉了！