Netty实现客户端和服务端的通信

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满心heo 2022-12-01 22:58:03

文章标签 Netty .net bootstrap json 文章分类 后端开发

Netty是Apache团队的又一个优秀的Socket框架，它和mina是一个团队开发的，所以很多思想是相同的，接下来，我们就来实现客户端和服务端的双向通信。

首先，我们定义消息类型：

/**
* 消息类型
* @author 李熠
*
*/
public enum MsgType {

PING,SEND,LOGIN,NO_TARGET

}
分别是心跳、发送、登录、找不到目标
当客户端和服务端连接后，需要向服务端发送登录请求，也就是消息类型：LOGIN，服务端接收到LOGIN请求后，会将客户端加入到队列中，

import java.io.Serializable;

public class Message implements Serializable {

private static final long serialVersionUID = -5756901646411393269L;

private String clientId;//发送者客户端ID

private MsgType type;//消息类型

private String data;//数据

private String targetId;//目标客户端ID

public String getTargetId() {
    return targetId;
}

public void setTargetId(String targetId) {
    this.targetId = targetId;
}

public String getClientId() {
    return clientId;
}

public void setClientId(String clientId) {
    this.clientId = clientId;
}

public MsgType getType() {
    return type;
}

public void setType(MsgType type) {
    this.type = type;
}

public String getData() {
    return data;
}

public void setData(String data) {
    this.data = data;
}

public Message(){

}

public Message(MsgType type){
    this.type = type;
}

}
这类是定义的消息Bean，想服务端发送消息就是发送的这个对象的数据。
接下来，实现客户端队列代码：

import io.netty.channel.Channel;
import io.netty.channel.socket.SocketChannel;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class NettyChannelMap {

private static Map<String , SocketChannel> map = new ConcurrentHashMap<>();

public static void add(String clientId,SocketChannel channel){
    map.put(clientId, channel);
}

public static Channel get(String clientId){
    return map.get(clientId);
}

public static void remove(SocketChannel channel){
    for (Map.Entry<String,SocketChannel> entry:map.entrySet()){
        if (entry.getValue()==channel){
            map.remove(entry.getKey());
        }
    }
}

}
服务端：
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.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.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.nio.charset.Charset;

public class NettyServer {

private int port;
public SocketChannel socketChannel;
public NettyServer(int port) throws InterruptedException {
    this.port = port;
    bind();
}

private void bind() throws InterruptedException {
    EventLoopGroup boss=new NioEventLoopGroup();
    EventLoopGroup worker=new NioEventLoopGroup();
    ServerBootstrap bootstrap=new ServerBootstrap();
    bootstrap.group(boss,worker);
    bootstrap.channel(NioServerSocketChannel.class);
    bootstrap.option(ChannelOption.SO_BACKLOG, 128);
    //通过NoDelay禁用Nagle,使消息立即发出去，不用等待到一定的数据量才发出去
    bootstrap.option(ChannelOption.TCP_NODELAY, true);
    //保持长连接状态
    bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true);
    bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
        @Override
        protected void initChannel(SocketChannel socketChannel) throws Exception {
            ChannelPipeline p = socketChannel.pipeline();
            //字符串类解析
    //这里只能添加字符串的编码和解码器，
    //网上有很多例子是这样写的：
    //这种写法只能所有客户端都用netty写，否则其他框架实现的客户端无法发送消息到服务端,因为他是转换的netty自己的Object
    //p.addLast(new ObjectEncoder());
      //p.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(this.getClass().getClassLoader())));   
            p.addLast(new StringEncoder(Charset.forName("UTF-8")));
            p.addLast(new StringDecoder(Charset.forName("UTF-8")));
            p.addLast(new NettyServerHandler());
        }
    });
    ChannelFuture f= bootstrap.bind(port).sync();
    if(f.isSuccess()){
        System.out.println("server start---------------");
    }
}
public static void main(String []args) throws InterruptedException {
    if(args.length == 0){
        new NettyServer(9999);
    }else{
        new NettyServer(Integer.parseInt(args[0]));
    }
}

}

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.SocketChannel;
import cn.sunsharp.netty.bean.Message;
import cn.sunsharp.netty.bean.MsgType;
import cn.sunsharp.netty.bean.NettyChannelMap;

import com.alibaba.fastjson.JSON;

//最好继承
SimpleChannelInboundHandler表示传递字符串消息，handler会把json格式的字符串转换为Message对象
public class NettyServerHandler extends SimpleChannelInboundHandler{@Override public void channelInactive(ChannelHandlerContext ctx) throws Exception { //channel失效，从Map中移除 NettyChannelMap.remove((SocketChannel)ctx.channel()); }@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)throws Exception {//cause.printStackTrace();System.out.println(“出现异常！”);}@Overrideprotected void messageReceived(ChannelHandlerContext ctx, String msg)throws Exception {System.out.println(msg);Message message = JSON.parseObject(msg+”“, Message.class);System.out.println(“接收到消息：”+message);String clientId = message.getClientId();if(MsgType.LOGIN.equals(message.getType())){System.out.printf(“将%s添加到队列\n”,clientId); NettyChannelMap.add(clientId,(SocketChannel)ctx.channel()); }else{ if(NettyChannelMap.get(clientId)==null){ System.out.printf(“登录失败，请重新登录!”,clientId); //说明未登录，或者连接断了，服务器向客户端发起登录请求，让客户端重新登录 message = new Message(MsgType.LOGIN); ctx.channel().writeAndFlush(JSON.toJSONString(message)); } } switch (message.getType()){ case PING:{ message = new Message(MsgType.PING); NettyChannelMap.get(clientId).writeAndFlush(JSON.toJSONString(message)); }break; case SEND:{ //收到客户端的请求，发送给targetId System.out.println(“发送消息：”+message); if(NettyChannelMap.get(message.getTargetId()) != null){ NettyChannelMap.get(message.getTargetId()).writeAndFlush(JSON.toJSONString(message)); }else{ message.setType(MsgType.NO_TARGET); NettyChannelMap.get(clientId).writeAndFlush(JSON.toJSONString(message)); } }break; default:break; }}}客户端可以使用任何框架任何语言的Socket来连接并发送消息，为了方便，这里依然用Netty来实现客户端：
import java.nio.charset.Charset;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.handler.timeout.IdleStateHandler;
import io.netty.util.concurrent.DefaultEventExecutorGroup;
import io.netty.util.concurrent.EventExecutorGroup;
import cn.sunsharp.regulation.bean.Message;
import cn.sunsharp.regulation.bean.MsgType;

import com.alibaba.fastjson.JSON;

public class NettyClient {

private int port;
private String host;
public SocketChannel socketChannel;
private static final EventExecutorGroup group = new DefaultEventExecutorGroup(20);
public NettyClient(int port, String host) {
    this.port = port;
    this.host = host;
    start();
}
private void start(){
    ChannelFuture future = null;
    try {
        EventLoopGroup eventLoopGroup=new NioEventLoopGroup();
        Bootstrap bootstrap=new Bootstrap();
        bootstrap.channel(NioSocketChannel.class);
        bootstrap.option(ChannelOption.SO_KEEPALIVE,true);
        bootstrap.group(eventLoopGroup);
        bootstrap.remoteAddress(host,port);
        bootstrap.handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel socketChannel) throws Exception {
                socketChannel.pipeline().addLast(new IdleStateHandler(20,10,0));
                socketChannel.pipeline().addLast(new StringEncoder(Charset.forName("UTF-8")));
                socketChannel.pipeline().addLast(new StringDecoder(Charset.forName("UTF-8")));
                socketChannel.pipeline().addLast(new NettyClientHandler());
            }
        });
        future =bootstrap.connect(host,port).sync();
        if (future.isSuccess()) {
            socketChannel = (SocketChannel)future.channel();
            System.out.println("connect server  成功---------");
        }else{
            System.out.println("连接失败！");
            System.out.println("准备重连！");
            start();
        }
    } catch (Exception e) {

    }finally{

// if(null != future){
// if(null != future.channel() && future.channel().isOpen()){
// future.channel().close();
// }
// }
// System.out.println(“准备重连！”);
// start();
}
}
public static void main(String[]args) throws InterruptedException {
NettyClient bootstrap=new NettyClient(9999,”192.168.1.38”);
System.out.println(11111);
Message loginMsg=new Message(MsgType.LOGIN);
loginMsg.setClientId(“001”);
loginMsg.setTargetId(“192.168.1.38”);
loginMsg.setType(MsgType.LOGIN);
bootstrap.socketChannel.writeAndFlush(JSON.toJSON(loginMsg));
}
}

import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.timeout.IdleStateEvent;
import cn.sunsharp.regulation.bean.Message;
import cn.sunsharp.regulation.bean.MsgType;

import com.alibaba.fastjson.JSON;

public class NettyClientHandler extends SimpleChannelInboundHandler {

public static ChannelHandlerContext context = null;

//利用写空闲发送心跳检测消息
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
    if (evt instanceof IdleStateEvent) {
        IdleStateEvent e = (IdleStateEvent) evt;
        switch (e.state()) {
            case WRITER_IDLE:
                Message pingMsg=new Message(MsgType.PING);
                ctx.writeAndFlush(JSON.toJSON(pingMsg));
                System.out.println("send ping to server----------");
                break;
            default:
                break;
        }
    }
}

@Override
protected void messageReceived(ChannelHandlerContext ctx, String msg)
        throws Exception {
    Message message = JSON.parseObject(msg+"", Message.class);
    MsgType msgType=message.getType();
    switch (msgType){
        case LOGIN:{
            //向服务器发起登录
            message = new Message(MsgType.LOGIN);
            ctx.writeAndFlush(JSON.toJSONString(message));
        }break;
        case PING:{
            System.out.println("receive ping from server----------");
        }break;
        case SEND:{
            //收到服务端消息
            System.out.println("收到服务端消息："+message.getData());
        }break;
        case NO_TARGET:{
            //收到服务端消息
            System.out.println("找不到targetId:"+message.getTargetId());
        }break;
        default:break;
    }
}