node-MQTT服務和環境 | Neko0xff tech blog

00 前置

本文會教使用者用nodejs來建立MQTT所需的環境和功能測試。

所需的函式庫
- Client: mqtt.js
```
$ npm install mqtt --save
```
- Server: Aedes bash $ npm install aedes --save

01 實做部分

1-1 Server: MQTT Broker

功能

主要管理己發布和訂閱的訊息
- 運作方式: 暫時儲存發布者(publisher)的訊息直到下回發布，只要在發布者中斷連線的情況下，就能即時提供訂閱者最近發布的訊息。

程式實作

mqttBroker.js

   /*MQTT Broker lib*/
   const aedes = require('aedes')();
   const server = require('net').createServer(aedes.handle);
   const port=3094; # 可自訂通訊埠

   /*啟動伺服端*/
  server.listen(port, function () {
     console.log('MQTT Server Started!');
     console.log('MQTT Server URL: http://[Server_IP]:'+port);
  });

1-2 Client

發布者（Publisher）: 向伺服器發送主題的一方

var mqtt = require("mqtt");
var Source = "mqtt://localhost:3094";
var client = mqtt.connect(Source);

/*連結後,不停發布temp的topic內容*/
client.on("connect", e => {
  console.log("success connect mqtt server");
  setInterval(() => {
    client.publish("temp", "25.6");
    console.log("send it");
  }, 1000);
});

訂閱者（Subscriber）: 從伺服器獲取主題的一方

    var mqtt = require("mqtt");
    var Source= "mqtt://localhost:3094";
    var client = mqtt.connect(Source);

    /*連結後,開始訂閱temp的topic內容*/
    client.on('connect', (e) => {
      console.log("success connect mqtt server");
      client.subscribe('temp', function (err) {
         console.log("subscribe temp topic")
      });
    });

   /* 輸出訂閱的內容*/
   client.on('message', function (topic, message) {
      // message is Buffer
      console.log(topic + ":\t" + message.toString())
   });

REF

CSDN

Other

https://www.emqx.com/en/blog/how-to-use-mqtt-in-nodejs