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最近看了一下&＃xff0c;mqtt,简单的做一下总结。

先说使用场景&＃xff0c;mqtt 适用于网络条件极端环境下使用&＃xff0c;对网络要求较低。比如物联网。另外也有一下比较高的可靠性&＃xff0c;比如最少有一次到达。

实现&＃xff1a;mqtt是使用字节来实现&＃xff0c;有什么报文什么的&＃xff0c;看了一头雾水。比较方便的是&＃xff0c;有一些第三方工具&＃xff0c;比如rabbitmq 提供的mqtt插件&＃xff0c;还有前端的mqtt.js&＃xff0c;各种工具&＃xff0c;使用起来和其他的mq没什么区别。

问题&＃xff1a;如果同时订阅两个topic,监听消息用几次

一下代码也是从别人那抄来的&＃xff0c;运行了一下&＃xff0c;没问题。需要用到nodejs

1、基础组件

npm install  koa --save

npm install mqtt --save

npm install jsdom --save

npm install mosac --save

生产端

var mqtt &＃61; require(&＃39;mqtt&＃39;);

var client &＃61; mqtt.connect(&＃39;mqtt://localhost:1883&＃39;);

client.on(&＃39;connect&＃39;, function () {

console.log(&＃39;>>> connected&＃39;)

// client.subscribe(&＃39;/tips&＃39;)

setInterval(

()&＃61;>{

var t&＃61; Math.floor(Math.random()*100);

client.publish(&＃39;/temperature&＃39;,t.toString());

},

3000

);

})

client.on(&＃39;message&＃39;, function (topic, message) {

// message is Buffer

console.log(message.toString())

})

node js  mq 组件

var mosca &＃61; require(&＃39;mosca&＃39;);

var ascoltatore &＃61; {

//using ascoltatore

// type: &＃39;mongo&＃39;,

// url: &＃39;mongodb://localhost:27017/mqtt&＃39;,

// pubsubCollection: &＃39;ascoltatori&＃39;,

// mongo: {}

};

var settings &＃61; {

port: 1883,

backend: ascoltatore

};

var server &＃61; new mosca.Server(settings);

server.on(&＃39;clientConnected&＃39;, function(client) {

console.log(&＃39;client connected&＃39;, client.id);

});

// fired when a message is received

server.on(&＃39;published&＃39;, function(packet, client) {

console.log(&＃39;Published&＃39;, packet.payload); //{"clientId":"mqttjs_02fea7b4","topic":"/tips"}

// console.log(&＃39;>>>packet&＃39;, packet); //{"clientId":"mqttjs_02fea7b4","topic":"/tips"}

});

server.on(&＃39;ready&＃39;, setup);

// fired when the mqtt server is ready

function setup() {

console.log(&＃39;Mosca server is up and running&＃39;);

}

消费端 &＃xff1a;

&＃39;use strict&＃39;

const mqtt &＃61; require(&＃39;mqtt&＃39;);

var client &＃61; mqtt.connect(&＃39;mqtt://localhost:1883&＃39;);

client.on(&＃39;connect&＃39;, function () {

console.log(&＃39;>>> connected&＃39;);

client.subscribe(&＃39;/temperature&＃39;);

})

client.on(&＃39;message&＃39;, function (topic, message) {

var temperature &＃61; parseInt(message.toString());

var data &＃61; {temperature};

if (temperature >&＃61; 60) {

data.tips &＃61; "热... 500服务器故障111";

}

else if (temperature >&＃61; 50) {

data.tips &＃61; "今天天气非常热&＃xff0c;建议不要穿衣服了";

}

else if (temperature >&＃61; 40) {

data.tips &＃61; "今天天气十分的热&＃xff0c;建议穿短袖T恤&＃43;短裤";

}

else if (temperature >&＃61; 30) {

data.tips &＃61; "今天天气有点的热&＃xff0c;建议穿短袖T恤";

}

else if (temperature >&＃61; 0) {

data.tips &＃61; "今天天气正好&＃xff0c;可以穿上一件薄衣服";

}

else if (temperature >&＃61; -10) {

data.tips &＃61; "今天天气十分寒冷&＃xff0c;棉袄可以穿上一件";

}

else {

data.tips &＃61; "今天天气十分十分寒冷&＃xff0c;棉袄可以穿上二件";

}

client.publish(&＃39;/tips&＃39;, JSON.stringify(data));

// if (temperature&＃43;1) {}

// message is Buffer

console.log(JSON.stringify(data));

})

在页面上展示

&＃39;use strict&＃39;

const Koa &＃61; require(&＃39;koa&＃39;);

const mqtt &＃61; require(&＃39;mqtt&＃39;);

const jsdom &＃61; require("jsdom");

const { JSDOM } &＃61; jsdom;

const { window } &＃61; new JSDOM(&＃96;&＃96;);

var $ &＃61; require(&＃39;jQuery&＃39;)(window);

const app &＃61; new Koa();

var msg &＃61; {temperature:"-",tips:""};

// response

app.use(ctx &＃61;> {

ctx.body &＃61; "

});

app.listen(3000);

//mqtt

var client &＃61; mqtt.connect(&＃39;mqtt://localhost:1883&＃39;);

client.on(&＃39;connect&＃39;, function () {

console.log(&＃39;>>> connected&＃39;);

client.subscribe(&＃39;/tips&＃39;);

})

client.on(&＃39;message&＃39;, function (topic, message) {

var data &＃61; JSON.parse(message.toString());

console.log(message.toString());

console.log(data.tips);

console.log(topic);

msg &＃61; data;

// if (temperature&＃43;1) {}

// message is Buffer

// let str &＃61; message.toString();

// let data &＃61; JSON.parse(message);

// console.log(data.tips);

// msg &＃61; message.toString();

})