.. vim: syntax=rst

.. highlight:: sh

Node
============================

本文主要介绍如何在 Node.js 项目中使用 MQTT.js 客户端库 ，实现 SX-IOT设备与 MQTT 服务器的连接、订阅、收发消息等功能。

前提条件
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

安装依赖包
------------------
.. code-block:: bash
   :linenos:

   sudo apt install nodejs npm -y
   npm install mqtt




连接使用
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
连接设置
------------------

本文将使用自定义的接入认证方式，服务器接入信息如下：

- Broker: **mqtt.geek-smart.cn**
- TCP Port: **1883**
- WebSocket Port: **8083**

导入依赖包
------------------
.. code-block:: js
   :linenos:

    const mqtt = require('mqtt')
    /** 
      choose which protocol to use for connection here 
       * TCP Port: 1883
       * WebSocket port: 8083
    */
    // tcp
    const { connectOptions } = require('./use_mqtt.js')
    // ws
    // const { connectOptions } = require('./use_ws.js')

定义连接地址、认证信息以及消息发布主题
------------------
.. code-block:: js
   :linenos:

    // tcp
    const connectOptions = {
      protocol: 'mqtt',
      port: 1883,
      host: 'mqtt.geek-smart.cn',
    }
    
    // ws
    // const connectOptions = {
    //   protocol: 'ws',
    //   port: 8083,
    //   host: 'mqtt.geek-smart.cn',
    // }
    
    module.exports = {
      connectOptions,
    }
    const pub_topic = '/HYUGHV/lVtAcHuorFDJ/4cebd60bfada/publish'
    const sub_topic = '/HYUGHV/lVtAcHuorFDJ/4cebd60bfada/subscribe'
    // tcp
    const clientId = 'nodejs-mqtt-tcp-client'
    // ws
    // const clientId = 'nodejs-mqtt-ws-client'
    const options = {
        clientId,
        clean: true,
        connectTimeout: 4000,
        username: 'OGVkSlBrskPY',
        password: 'XaIkqRXwcNuuQjXGPi',
        reconnectPeriod: 1000,
    }

定义消息发布函数
------------------
.. code-block:: js
   :linenos:

    client.publish(pub_topic, payload, { qos }, (error) => {
        if (error) {
            console.error(error)
        }
    })


定义 on_message 回调函数，用于打印订阅主题接收的消息内容
------------------------------------------------------------------------

.. code-block:: js
   :linenos:

    client.on('message', (sub_topic, payload) => {
        console.log('Received Message:', sub_topic, payload.toString())
    })

连接 MQTT
------------------------------------------------------------------------
.. code-block:: js
   :linenos:

    client.on('connect', () => {
        console.log(`${protocol}: Connected`)
    })


完整代码
------------------------------------------------------------------------
.. code-block:: js
   :linenos:

    const mqtt = require('mqtt')
        /** 
          choose which protocol to use for connection here 
           * TCP Port: 1883
           * WebSocket port: 8083
        */
        // tcp
    const { connectOptions } = require('./use_mqtt.js')
        // ws
        // const { connectOptions } = require('./use_ws.js')

    const clientId = 'nodejs-mqtt-tcp-client'
        // const clientId = 'nodejs-mqtt-ws-client'
    const options = {
        clientId,
        clean: true,
        connectTimeout: 4000,
        username: 'OGVkSlBrskPY',
        password: 'XaIkqRXwcNuuQjXGPi',
        reconnectPeriod: 1000,
    }

    const { protocol, host, port } = connectOptions
    /**
     * if protocol is "mqtt", connectUrl = "mqtt://mqtt.geek-smart.cn:1883"
     * if protocol is "ws", connectUrl = "ws://mqtt.geek-smart.cn:8083/mqtt"
     *
     * for more details about "mqtt.connect" method & options,
     * please refer to https://github.com/mqttjs/MQTT.js#mqttconnecturl-options
     */
    let connectUrl = `${protocol}://${host}:${port}`
    if (['ws', 'wss'].includes(protocol)) {
        // mqtt: MQTT-WebSocket uniformly uses /path as the connection path,
        // which should be specified when connecting, and the path used on EMQX is /mqtt.
        connectUrl += '/mqtt'
    }

    const client = mqtt.connect(connectUrl, options)

    const pub_topic = '/HYUGHV/lVtAcHuorFDJ/4cebd60bfada/publish'
    const sub_topic = '/HYUGHV/lVtAcHuorFDJ/4cebd60bfada/subscribe'
    const payload = '{"type":"info"}'
        // https://github.com/mqttjs/MQTT.js#qos
    const qos = 0

    // https://github.com/mqttjs/MQTT.js#event-connect
    client.on('connect', () => {
        console.log(`${protocol}: Connected`)

        // subscribe topic
        // https://github.com/mqttjs/MQTT.js#mqttclientsubscribetopictopic-arraytopic-object-options-callback
        client.subscribe(sub_topic, { qos }, (error) => {
            if (error) {
                console.log('subscribe error:', error)
                return
            }
            console.log(`${protocol}: Subscribe to topic '${sub_topic}'`)
                // publish message
                // https://github.com/mqttjs/MQTT.js#mqttclientpublishtopic-message-options-callback
            client.publish(pub_topic, payload, { qos }, (error) => {
                if (error) {
                    console.error(error)
                }
            })
        })
    })

    // https://github.com/mqttjs/MQTT.js#event-reconnect
    client.on('reconnect', (error) => {
        console.log(`Reconnecting(${protocol}):`, error)
    })

    // https://github.com/mqttjs/MQTT.js#event-error
    client.on('error', (error) => {
        console.log(`Cannot connect(${protocol}):`, error)
    })

    // https://github.com/mqttjs/MQTT.js#event-message
    client.on('message', (sub_topic, payload) => {
        console.log('Received Message:', sub_topic, payload.toString())
    })

    /**
     * If you need to unsubscribe from a topic, you can use the following code.
     */
    // // unsubscribe topic
    // // https://github.com/mqttjs/MQTT.js#mqttclientunsubscribetopictopic-array-options-callback
    // client.unsubscribe(sub_topic, { qos }, (error) => {
    //   if (error) {
    //     console.log('unsubscribe error:', error)
    //     return
    //   }
    //   console.log(`unsubscribed topic: ${sub_topic}`)
    // })

    /**
     * If you need to disconnect, you can use the following code.
     */
    // if (client.connected) {
    //   try {
    //     // disconnect
    //     // https://github.com/mqttjs/MQTT.js#mqttclientendforce-options-callback
    //     client.end(false, () => {
    //       console.log('disconnected successfully')
    //     })
    //   } catch (error) {
    //     console.log('disconnect error:', error)
    //   }
    // }


测试验证
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

运行
------------------------------------------------------------------------
.. code-block:: bash
   :linenos:

   npm start