微信小程序连接MQTT服务器、阿里云微消息队列MQTT版

微信小程序连接阿里云微消息队列MQTT版，（多看几遍文档）

https://help.aliyun.com/document_detail/59721.html

连接的参数：

1. client id (GID_XXX@@@YYY)

2. 用户名 (Signature|xxx|xxx)

3. 密码（根据阿里云规则计算，使用 hex_hmac_sha1.js 计算）

4. const client = mqtt.connect('wx://xxx.mqtt.aliyuncs.com', options)

5. 关于topic，主topic例如‘test’，子topic可以是‘test/test2’

打开 https://unpkg.com/browse/mqtt@2.18.8/dist/mqtt.min.js 复制保存为js文件并且引入该文件

const mqtt = require('../../utils/mqtt.min.js')

function connectMqtt() {
  const options = {
    connectTimeout: 30000,
    keepalive: 120,
    clientId: '12345678',
    username: 'xxx',
    password: 'xxx',
  }
  const client = mqtt.connect('wxs://x.x.x.x', options)
 
  client.on('reconnect', (error) => {
    console.log('mqtt on reconnect:', error)
  })
 
  client.on('disconnect', (e) => {
    console.log('mqtt on disconnect')
  })
 
  client.on('error', (error) => {
    console.log('mqtt on error:', error)
  })
 
  client.on('connect', (e) => {
    console.log('mqtt on connect')
    client.subscribe('test', { qos: 0 }, function (err) {
        if (!err) {
          console.log("mqtt sub success")
        }
    })
  })
 
  client.on('message', function (topic, message, packet) {
    var payload = packet.payload.toString()
    console.log("mqtt on message:", payload)
    if (payload == 'server_cmd_send_test') {
      client.publish('test2', "send_test from minip");
    }
  })

}