物联网 基于netty构建mqtt协议规范(发布/订阅模式)
简述
提供一对多的消息分发和消息生产/消费方的解耦，发布者无需知道订阅者的存在，两者通过 Broker 间接通信
源码(netty-sample-03-PubSub)
https://gitee.com/kcnf-iot/iot-sample/tree/master/netty/netty-sample-03
核心角色与工作流程
| 角色 | 职责 |
|---|---|
| 订阅者（Subscriber） | 向 Broker 发送 SUBSCRIBE 请求，注册对某个主题的兴趣；接收来自 Broker 的推送消息。 |
| 发布者（Publisher） | 向 Broker 发送 PUBLISH 请求，将消息发送到指定主题。 |
| Broker（代理） | 维护主题与订阅者列表的映射；接收发布的消息，并转发给对应主题的所有订阅者。 |
整体流程
┌─────────────┐ ┌──────────────┐ ┌──────────────┐
│ Publisher │ ──────► │ Broker │ ◄────── │ Subscriber │
│ (8888) │ 发布 │ (消息总线) │ 订阅 │ (9999) │
└─────────────┘ └──────────────┘ └──────────────┘
端口: 7777sub代码
package com.jysemel.iot.subscriber;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;
public class SubscriberServer {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(group)
.channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) {
ChannelPipeline p = ch.pipeline();
p.addLast(new LineBasedFrameDecoder(1024));
p.addLast(new StringDecoder(StandardCharsets.UTF_8));
p.addLast(new StringEncoder(StandardCharsets.UTF_8));
p.addLast(new SubscriberHandler());
}
});
ChannelFuture future = bootstrap.connect("127.0.0.1", 7777).sync();
System.out.println("===========================================");
System.out.println(" Subscriber 客户端已启动");
System.out.println("===========================================");
System.out.println("已连接到 Broker: 127.0.0.1:7777");
System.out.println("功能: 订阅主题并接收消息");
System.out.println("命令格式: SUB <topic>");
System.out.println("示例: SUB news");
System.out.println("输入 'quit' 退出");
System.out.println("===========================================\n");
Channel channel = future.channel();
Scanner scanner = new Scanner(System.in);
while (true) {
String input = scanner.nextLine();
if ("quit".equalsIgnoreCase(input)) {
break;
}
channel.writeAndFlush(input + "\n");
}
} finally {
group.shutdownGracefully();
}
}
}broker代码
package com.jysemel.iot.broker;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
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.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import java.nio.charset.StandardCharsets;
public class BrokerServer {
public void start() throws InterruptedException {
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap bootstrap = new ServerBootstrap();
bootstrap.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) {
ChannelPipeline p = ch.pipeline();
p.addLast(new LineBasedFrameDecoder(1024));
p.addLast(new StringDecoder(StandardCharsets.UTF_8));
p.addLast(new StringEncoder(StandardCharsets.UTF_8));
p.addLast(new BrokerHandler());
}
});
ChannelFuture future = bootstrap.bind(7777).sync();
System.out.println("===========================================");
System.out.println(" Broker 服务器启动");
System.out.println("===========================================");
System.out.println("端口: 7777");
System.out.println("功能: 消息路由和分发（充当 Redis 角色）");
System.out.println("支持命令:");
System.out.println(" - PUB <topic> <message> : 发布消息");
System.out.println(" - SUB <topic> : 订阅主题");
System.out.println(" - UNSUB <topic> : 取消订阅");
System.out.println("===========================================\n");
future.channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws InterruptedException {
new BrokerServer().start();
}
}pub代码
package com.jysemel.iot.publisher;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;
public class PublisherServer {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(group)
.channel(NioSocketChannel.class)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) {
ChannelPipeline p = ch.pipeline();
p.addLast(new LineBasedFrameDecoder(1024));
p.addLast(new StringDecoder(StandardCharsets.UTF_8));
p.addLast(new StringEncoder(StandardCharsets.UTF_8));
p.addLast(new PublisherHandler());
}
});
ChannelFuture future = bootstrap.connect("127.0.0.1", 7777).sync();
System.out.println("===========================================");
System.out.println(" Publisher 客户端已启动");
System.out.println("===========================================");
System.out.println("已连接到 Broker: 127.0.0.1:7777");
System.out.println("功能: 发布消息到指定主题");
System.out.println("命令格式: PUB <topic> <message>");
System.out.println("示例: PUB news Hello World");
System.out.println("输入 'quit' 退出");
System.out.println("===========================================\n");
Channel channel = future.channel();
Scanner scanner = new Scanner(System.in);
while (true) {
String input = scanner.nextLine();
if ("quit".equalsIgnoreCase(input)) {
break;
}
channel.writeAndFlush(input + "\n");
}
} finally {
group.shutdownGracefully();
}
}
}验证结果
