Netty-使用netty实现群聊-代码实现

1、功能介绍

和之前的NIO实现群聊机制一样，这里使用Netty实现：

• 1、当有新用户上线时，通知其他用户上线，下线同理
• 2、用户x发送一条消息，服务器端转发给其他所有在线服务器

2、代码结构

3、GroupChatServer

package groupchat;

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.string.StringDecoder;

import java.beans.Encoder;

public class GroupChatServer {
    //监听端口
    private int port;

    public GroupChatServer(int port){
        this.port = port;
    }

    //编写run方法，处理客户端的请求
    public void run() throws Exception{
        //创建两个线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        //其中NioEventLoppGroup默认八个线程
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            //创建ServerBootstrap,服务器启动引导类
            ServerBootstrap b = new ServerBootstrap();
            //设置ServerBootstrap相关参数
            b.group(bossGroup, workerGroup)//roup函数设置两个EventLoop
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {//指定相关handler
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            //获取pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //向pipeline中加入解码器
                            pipeline.addLast("decoder", new StringDecoder());
                            //向pipeline中加入编码器
                            pipeline.addLast("encoder", new StringDecoder());
                            //加入自己的业务处理handler,需要自己写！关键部分
                            pipeline.addLast(new GroupChatServerHandler());
                        }
                    });
            System.out.println("Netty服务器已启动");
            ChannelFuture channelFuture = b.bind(port).sync();
            //监听关闭事件
            channelFuture.channel().closeFuture().sync();
        }finally {
            //关闭
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
    }

    }

    //主函数,也需要抛出异常
    public static void main(String[] args) throws Exception{
        //启动一个服务器
        new GroupChatServer(7000);
    }
}

4、GroupChatServerHandler

package groupchat;

import io.netty.channel.Channel;
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;

import java.text.SimpleDateFormat;
import java.util.SimpleTimeZone;

public class GroupChatServerHandler extends SimpleChannelInboundHandler<String> {
    //定义一个channelle组，管理所有的channel
    //GlobalEventExecutor.INSTANCE是全局的时间执行器，是一个单例，帮助执行channelGroup
    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
    //输出接收到消息的时间用
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    //当连接建立之后，第一个被执行，将当前的channel加入到channelGroup
    @Override
    public  void handlerAdded(ChannelHandlerContext ctx) throws Exception{
        Channel channel = ctx.channel();
        //将该客户端加入聊天的消息  发送给其他的在线客户端
        //writeAndFlush方法会自动遍历所有的channel,并发送括号内消息
        //最后加入当前消息发送的时间
        channelGroup.writeAndFlush("客户端" + channel.remoteAddress() + "加入聊天\n"
                + sdf.format(new java.util.Date()) + "\n");
        //channelGroup中加入该channel
        channelGroup.add(channel);
    }

    //断开连接，触发该通知给当前在线的客户
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channelGroup.writeAndFlush("客户端" + channel.remoteAddress() + "离开聊天了\n");
        System.out.println("测试用："+"channelGroup_size=" + channelGroup.size() );
    }

    //channel出于活动状态，提示xxx已上线
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception{
        System.out.println(ctx.channel().remoteAddress() + "上线");
    }

    //提示xxx离线
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception{
        System.out.println(ctx.channel().remoteAddress() + "离线了");
    }

    //读取数据并转发数据给当前在线的其他客户端
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String s) throws Exception {
        //获取当前channel
        //给自己发送的消息是不一样的
        final Channel channel = channelHandlerContext.channel();
        //根据不同的情况，需要会送不同的消息
        channelGroup.forEach(ch -> {
            if(channel != ch)
                ch.writeAndFlush("[客户]" + channel.remoteAddress() + "发送了消息：" + s + "\n");
            else
                ch.writeAndFlush("[自己]" + "发送了消息：" + s + "\n");
        });
    }

    //发生异常时
    @Override
    public void exceptionCaught(ChannelHandlerContext var1, Throwable var2) throws Exception{
        //关闭通道
        var1.close();
    }

}

5、GroupChatClient

package groupchat;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.pool.ChannelPool;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import javax.naming.event.EventContext;
import java.awt.*;
import java.util.Scanner;

public class GroupChatClient {
    //主机地址
    private final String host;
    //端口
    private final int port;

    public GroupChatClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public void run() throws Exception{
        EventLoopGroup eventExecutors = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap()
                    .group(eventExecutors)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected  void initChannel(SocketChannel ch) throws Exception{
                            //得到pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //加入相关handler
                            pipeline.addLast("decoder",new StringDecoder());
                            pipeline.addLast("encoder",new StringEncoder());
                            //加入自定义handler
                            pipeline.addLast(new GroupChatServerHandler());
                        }
                    });
            ChannelFuture channelFuture = bootstrap.connect(host,port).sync();
            //得到当前channel
            Channel channel = channelFuture.channel();
            System.out.println("......" + channel.localAddress() + "......");

            //客户端需要输入信息，使用Scanner扫描器
            Scanner scanner = new Scanner(System.in);
            while(scanner.hasNextLine()){
                String msg = scanner.nextLine();
                //将消息通过channel发送给服务器端
                channel.writeAndFlush(msg + "\r\n");
            }
        }finally {
            eventExecutors.shutdownGracefully();
        }
    }

    //客户端主函数
    public static void main(String[] args) throws Exception {
        new GroupChatClient("127.0.0.1",7000).run();
    }
}

6、GroupChatClientHandler

package groupchat;

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

public class GroupChatClientHandler extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        System.out.println(msg.trim());
    }
}

7、测试方法

• 1）新建一个Maven工程，导入netty依赖
• 2）按照2结构搭建代码
• 3）运行服务器端GroupChatServer
• 4）运行一个客户端GroupChatClient，再切换端口运行新的客户端，进行测试，收发消息/通知与否

8、遇到的问题

遇到Exception异常Exception in thread "main" io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: no further information: /127.0.0.1:53853
应该是IP或者端口设置错了，尝试设置一下本地计算机