鸿蒙OS开发实例：【ArkTS 实现MQTT协议】

介绍

MQTT是物联网中的一种协议，在HarmonyOS API9平台，解决方案以C++库移植为实现方案。

遥遥领先的平台，使用MQTT怎能不遥遥领先呢！

新年快乐，本篇将带领你手把手实现HarmonyOS ArkTS语言的MQTT协议。

准备

1. 阅读MQTT 5.0协议
2. 安装Mosquitto服务器
3. MQTT 联盟中的中国成员实现的PC版客户端 参考文档：qr23.cn/AKFP8k

效果

HarmonyOS MQTT实现概况

业务流程

页面与功能实现类

MQTT 实现路线

MQTT协议最大的好处是纯软件协议, 不像Zigbee协议还会和硬件相关，所以在实现MQTT协议前，我们只需要专注于两件事情：

1. MQTT协议传输通道
2. MQTT协议格式

通道即传输数据的载体，这里指的是Sokect, 了解HarmonyOS平台的Sokect使用方法尤为重要。

数据传输通道打通之后，需要专注于MQTT协议格式的实现。

由于之前对MQTT协议有所了解，所以在HarmonyOS 平台中看到Socket时，觉得在这个新平台上实现MQTT协议理论上没有任何问题，所以最终决定干它。

下边这张图是实现HarmonyOS MQTT协议的过程，仅作参考。

MQTT资深专家，只需要阅读关于HarmonyOS Socket的API 和 TypeScript 操作字节的一些基础内容即可

​

MQTT协议介绍

一) MQTT共有15种协议

1. CONNECT
2. CONNACK
3. PUBLISH
4. PUBACK
5. PUBREC
6. PUBREL
7. PUBCOMP
8. DISCONNECT
9. PINGREQ
10. PINGRES
11. SUBSCRIBE
12. SUBACK
13. UNSUBSCRIBE
14. UNSUBACK
15. AUTH

二）MQTT共有7种数据格式

这些数据格式名称会在MQTT技术规范中作为标准用语使用

1. one Byte
2. Two Byte
3. Four Byte
4. UTF-8 String
5. UTF-8 String Pair
6. Variable Byte Integer
7. Binary Data

数据格式实现

数据格式稍微看一下即可

详情可参见MQTT V5.0规范文档

关于数据格式文档可以查找关键词 "1.5 Data representation"

Two Byte

比如数字2，如果要编码为两个字节，则调用twoByte方法即可

twoByte(2)

public static twoByte(content: number): Uint8Array{
   return new Uint8Array([(content & 0xff00) >> 8 , content & 0xff])
}

Four Byte

比如数字2，如果要编码为四个字节，则调用

fourByte(2)

public static fourByte(content: number): Uint8Array{
  return new Uint8Array([(content & 0xff000000) >> 24 ,(content & 0xff0000) >> 16, (content & 0xff00) >> 8 , content & 0xff])
}

UTF-8 String

比如数字2，如果要采用UTF-8编码，则调用

utf8String(2)

public static utf8String(content: string): Uint8Array{
  const encoder = new util.TextEncoder()
  let u8a_encoder = encoder.encodeInto(content)

  let encoderLength = u8a_encoder.length

  let abEncoder = new ArrayBuffer(encoderLength + 2)
  const dv_encoder = new DataView(abEncoder)
  dv_encoder.setInt8(0, (encoderLength & 0xff00) >> 8)
  dv_encoder.setInt8(1, encoderLength & 0x00ff)

  let index: number = 2
  u8a_encoder.forEach( (value) => {
    dv_encoder.setInt8(index++, value)
  })

  return new Uint8Array(abEncoder)
}

UTF-8 String Pair

比如Key为'Key-Hello'，Value为'Value-World'如果要采用Key-Value方式的UTF-8编码，则调用

utf8StringPair('Key-Hello','Value-World')

public static utf8StringPair(key: string, value: string): Uint8Array{
  let u8a_key = this.utf8String(key)
  let u8a_value = this.utf8String(value)

  let merge = new Uint8Array(u8a_key.length + u8a_value.length)
  merge.set(u8a_key)
  merge.set(u8a_value, u8a_key.length)
  return merge
}

Variable Byte Integer

可变字节编码，这种编码方式的最大长度是4个字节。

所以，用1～4个字节可动态编码相关数字，实现节省占用内存的目标

比如数字2，编码完成后，只会占用一个字节

encodeVariableByteInteger(2)

public static encodeVariableByteInteger(content: number): Uint8Array {

  let cacheDigit = new Array<number>()

  let numBytes: number = 0
  let no: number = content

  do {
    let digit = no % 128
    no = parseInt(no / 128 +'', )
    if (no > 0) {
      digit |= 0x80
    }
    cacheDigit.push(digit)
    numBytes++
  } while ( (no > 0) && (numBytes < 4) )

  return new Uint8Array(cacheDigit)
}

Binary Data

这种数据格式是由2字节和剩余的字节数组组成，除2个字节之外的字节数组在解码时，需要按照约定来解码。

比如想要表达数字2，则调用

binaryData(new Uint8Array([2]))

public static binaryData(ext: Uint8Array): Uint8Array{
  let length = ext.length

  let u8a_binaryData = new Uint8Array(2 + length)

  u8a_binaryData[0] = (length & 0xff00) >> 8
  u8a_binaryData[1] = length & 0x00ff

  let index: number = 2
  ext.forEach((value)=>{
    u8a_binaryData[index++] = value
  })

  return u8a_binaryData
}

HarmonyOS Socket

[HarmonyOS 指南]

鸿蒙OS开发	更多内容↓点击	HarmonyOS 与OpenHarmony技术
鸿蒙技术文档	《鸿蒙NEXT星河版开发学习文档》

1）包引入

注意：这个包在编译时，DevEco Studio 会提示警告，但官方资料中并未做说明

import socket from '@ohos.net.socket';

2）创建Socket

// 创建一个TCPSocket连接，返回一个TCPSocket对象。

let tcp = socket.constructTCPSocketInstance();

3) 注册Socket事件消息

• 连接事件
• 接收消息事件
• Socket关闭事件
• 错误事件

tcp.on('message', value => {  
       console.log("on message")  
       let buffer = value.message  
       let dataView = new DataView(buffer)  
       let str = ""  
       for (let i = 0; i < dataView.byteLength; ++i) {    
          str += String.fromCharCode(dataView.getUint8(i))  
       }  
        console.log("on connect received:" + str)
     });
     
tcp.on('connect', () => {  console.log("on connect")});

tcp.on('close', () => {  console.log("on close")});

tcp.on('error', () => {  console.log("on error")});

4) 绑定本地端口

// 绑定IP地址和端口。
let bindAddress = {
  address: '192.168.xx.xx',
  port: 1234, // 绑定端口，如1234
  family: 1
};
tcp.bind(bindAddress, err => {
  if (err) {
    console.log('bind fail');
    return;
  }
  console.log('bind success');
  
  //TODO 连接服务端代码
  ......

});

5) 连接Broker服务器

// 绑定IP地址和端口。
let bindAddress = {
  address: '192.168.xx.xx',
  port: 1234, // 绑定端口，如1234
  family: 1
};
tcp.bind(bindAddress, err => {
  if (err) {
    console.log('bind fail');
    return;
  }
  console.log('bind success');
  
  let connectAddress = {
     address: '192.168.xx.xx',
     port: 5678, // 连接端口，如5678
    family: 1
  };
  tcp.connect({
      address: connectAddress, timeout: 6000
      }, err => {
        if (err) {
         console.log('connect fail');
         return;
        }
      console.log('connect success');
  
      // 发送数据
      tcp.send({
          data: 'Hello, server!'
         }, err => {
           if (err) {
              console.log('send fail');
              return;
            }
          console.log('send success');
       })
   });
});

MQTT 协议实现一瞥

• 协议的实现过程，需要对照MQTT V5.0规范逐条实现。
• 切不可操之过急
• 发布一条消息和接收一条消息用到的协议都是PUBLISH

CONNECT协议

如下代码即为CONNECT协议实现的源码

Socket通道创建成功之后，仅仅代表客户端与服务端已经建立了消息通道，但这条通道是否可以使用，就需要用到"连接"协议，简单点的讲：客户端和服务端开始通信，交流的规则肯定是一致的。

从如下CONNECT协议实现源码注释中可见，一个通信包包含3个部分：1. 固定头（Fixed Header） 2. 可变头（Variable Header）3. 负载体(PayLoad)

注意：固定头表示由两部分组成，第一部分为一个字节，表示数据包类型和其它预留属性，第二部分表示数据包除第一个字节和自己所占用的字节以外，还剩余多少个字节，用于数据包解码参照计算。第二部分的字节长度数据类型为Variable Byte Integer，因此，其可能占用1～4个字节

import ArrayList from '@ohos.util.ArrayList';
import HashMap from '@ohos.util.HashMap';
import util from '@ohos.util';
import MQTTCommon from '../common/MQTTCommon';
import MqttDataTypes from '../common/MqttDataTypes';

//3.1 CONNECT -- Connection Request
export default class MQTTConnect{

  //3.1.1 CONNECT Fixed Header 【1字节 + Variable Byte Integer】
  //3.1.2 CONNECT Variable Header
      //3.1.2.1 Protocol Name 【6字节】
      //3.1.2.2 Protocol Version 【1字节】
      //3.1.2.3 Connect Flags 【1字节】
      //3.1.2.10 Keep Alive 【2字节】
      //3.1.2.11 CONNECT Properties
          //3.1.2.11.1 Property Length 【1字节】
          //3.1.2.11.2 Session Expiry Interval 【4字节】
          //3.1.2.11.3 Receive Maximum 【2字节】
          //3.1.2.11.4 Maximum Packet Size 【4字节】
          //3.1.2.11.5 Topic Alias Maximum 【2字节】
          //3.1.2.11.6 Request Response Information 【1字节】
          //3.1.2.11.7 Request Problem Information 【1字节】
          //3.1.2.11.8 User Property【UTF-8 String Pair】
          //3.1.2.11.9 Authentication Method 【UTF-8 String】
          //3.1.2.11.10 Authentication Data【Binary Data】
  //3.1.3 CONNECT Payload
      //3.1.3.1 Client Identifier (ClientID) 【UTF-8 String】
      //3.1.3.2 Will Properties
          //3.1.3.2.1 Property Length 【Variable Byte Integer】
          //3.1.3.2.2 Will Delay Interval 【4字节】
          //3.1.3.2.3 Payload Format Indicator 【1字节】
          //3.1.3.2.4 Message Expiry Interval 【4字节】
          //3.1.3.2.5 Content Type【UTF-8 String】
          //3.1.3.2.6 Response Topic【UTF-8 String】
          //3.1.3.2.7 Correlation Data 【Binary Data】
          //3.1.3.2.8 User Property【UTF-8 String Pair】
     //3.1.3.3 Will Topic 【UTF-8 String】
     //3.1.3.4 Will Payload【Binary Data】
     //3.1.3.5 User Name【UTF-8 String】
     //3.1.3.6 Password【Binary Data】
  //3.1.4 CONNECT Actions

   private connectFlag: number = 0b00000000
   private keepAlive: number = 3600
   private sessionExpiryInterval: number = 3600
   private receiveMaximum: number = 10000
   private topicAliasMaximum: number = 10
   private maximumPacketSize: number = 10000
   private requestResponseInformation: number = 1
   private requestProblemInformation: number = 1
   private clientIdentifier: string = ''
   private authenticationMethod: string = ''
   private authenticationData: string = ''
   private userProperties: HashMap<string, string> = new HashMap()
   private willDelayInterval: number = 0
   private payloadFormatIndicator: number = 1
   private messageExpiryInterval: number = 3600
   private contentType: string = ''
   private responseTopic: string = ''
   private willTopic: string = ''
   private correlationData: string = ''
   private willPayload: string = ''
   private userName: string = ''
   private passWord: string = ''
   private willUserProperties: HashMap<string, string> = new HashMap()

   public static create(): MQTTConnect{
      return new MQTTConnect()
   }

   public setTopicAliasMaximum(topicAliasMaximum: number){
      this.topicAliasMaximum = topicAliasMaximum
      return this
   }

   public setWillUserProperties(willUserProperties: HashMap<string, string>){
      this.willUserProperties = willUserProperties
      return this
   }

   public setUserName(userName: string){
      this.userName = userName
      return this
   }

   public setPassWord(passWord: string){
      this.passWord = passWord
      return this
   }

   public setWillPayload(willPayload: string){
      this.willPayload = willPayload
      return this
   }

   public setCorrelationData(correlationData: string){
      this.correlationData = correlationData
      return this
   }

   public setWillTopic(willTopic: string){
      this.willTopic = willTopic
      return this
   }

   public setResponseTopic(responseTopic: string){
      this.responseTopic = responseTopic
      return this
   }

   public setContentType(contentType: string){
      this.contentType = contentType
      return this
   }

   public setKeepAlive(keepAlive: number){
      this.keepAlive = keepAlive
      return this
   }

   public setSessionExpiryInterval(sessionExpiryInterval: number){
      this.sessionExpiryInterval = sessionExpiryInterval
      return this
   }

   public setReceiveMaximum(receiveMaximum: number){
      this.receiveMaximum = receiveMaximum
      return this
   }

   public setMaximumPacketSize(maximumPacketSize: number){
      this.maximumPacketSize = maximumPacketSize
      return this
   }

   public setRequestResponseInformation(requestResponseInformation: number){
      this.requestResponseInformation = requestResponseInformation
      return this
   }

   public setRequestProblemInformation(requestProblemInformation: number){
      this.requestProblemInformation = requestProblemInformation
      return this
   }

   public setAuthenticationMethod(authenticationMethod: string){
      this.authenticationMethod = authenticationMethod
      return this
   }

   public setAuthenticationData(authenticationData: string){
      this.authenticationData = authenticationData
      return this
   }

   public setUserProperties(m: HashMap<string, string>){
      this.userProperties = m
      return this
   }

   public setClientIdentifier(clientIdentifier: string){
      this.clientIdentifier = clientIdentifier
      return this
   }

   public setWillDelayInterval(willDelayInterval: number){
      this.willDelayInterval = willDelayInterval
      return this
   }

   public setPayloadFormatIndicator(payloadFormatIndicator: number){
      this.payloadFormatIndicator = payloadFormatIndicator
      return this
   }

   public setMessageExpiryInterval(messageExpiryInterval: number){
      this.messageExpiryInterval = messageExpiryInterval
      return this
   }

   //User Name Flag | Password Flag | Will Retain | Will QoS | Will Flag | Clean Start | Reserved
   public setConnectFlag(flag: number){
      this.connectFlag = flag
   }

   public buildPacket(): Uint8Array{
      let allData = new ArrayList<Uint8Array>()

      let remainLength: number = 0

      //3.1.1 CONNECT Fixed Header - 包类型
      let u8a_packettype = MqttDataTypes.oneByte(MQTTCommon.PACKET_TYPE_REQ_CONNECT << 4)
      allData.add(u8a_packettype)

      //3.1.2 CONNECT Variable Header
      //3.1.2.1 Protocol Name
      let u8a_protolName = MqttDataTypes.utf8String('MQTT')
      allData.add(u8a_protolName)
      remainLength += u8a_protolName.length

      //3.1.2.2 Protocol Version
      let u8a_version = MqttDataTypes.oneByte(5)
      allData.add(u8a_version)
      remainLength++

      //3.1.2.3 Connect Flags
      let willFlag = this.connectFlag&0b00001000
       if(willFlag==0){
          //User Name Flag | Password Flag | Will Retain | Will QoS | Will Flag | Clean Start | Reserved
          //bit7             bit6            bit5          bit4~bit3  bit2        bit1           bit0
          //QoS强制设置为0
          //WillRetain强制设置为0
          this.connectFlag = this.connectFlag&0b11000111
       }

      let u8a_connectFlags = MqttDataTypes.oneByte(this.connectFlag)
      allData.add(u8a_connectFlags)
      remainLength += u8a_connectFlags.length

      //3.1.2.10 Keep Alive
      let u8a_keepalive = MqttDataTypes.twoByte(this.keepAlive)
      allData.add(u8a_keepalive)
      remainLength += u8a_keepalive.length

      //3.1.2.11 CONNECT Properties
      let propertiesLength: number = 0
      let insertStartIndex: number = allData.length

      //3.1.2.11.2 Session Expiry Interval
      let u8a_sessionexpiryintervaltype = MqttDataTypes.oneByte(0x11)
      allData.add(u8a_sessionexpiryintervaltype)
      propertiesLength += u8a_sessionexpiryintervaltype.length

      let u8a_sessionexpiryinterval = MqttDataTypes.fourByte(this.sessionExpiryInterval)
      allData.add(u8a_sessionexpiryinterval)
      propertiesLength += u8a_sessionexpiryinterval.length

      //3.1.2.11.3 Receive Maximum
      let u8a_receiveMaximumType = MqttDataTypes.oneByte(0x21)
      allData.add(u8a_receiveMaximumType)
      propertiesLength += u8a_receiveMaximumType.length

      let u8a_receiveMaximum = MqttDataTypes.twoByte(this.receiveMaximum)
      allData.add(u8a_receiveMaximum)
      propertiesLength += u8a_receiveMaximum.length

      //3.1.2.11.4 Maximum Packet Size
      let u8a_maximumPacketSizeType = MqttDataTypes.oneByte(0x27)
      allData.add(u8a_maximumPacketSizeType)
      propertiesLength += u8a_maximumPacketSizeType.length

      let u8a_maximumPacketSize = MqttDataTypes.fourByte(this.maximumPacketSize)
      allData.add(u8a_maximumPacketSize)
      propertiesLength += u8a_maximumPacketSize.length

      //3.1.2.11.5 Topic Alias Maximum
      let u8a_topicAliasMaximumType = MqttDataTypes.oneByte(0x22)
      allData.add(u8a_topicAliasMaximumType)
      propertiesLength += u8a_topicAliasMaximumType.length

      let u8a_topicAliasMaximum = MqttDataTypes.twoByte(this.topicAliasMaximum)
      allData.add(u8a_topicAliasMaximum)
      propertiesLength += u8a_topicAliasMaximum.length

      //3.1.2.11.6 Request Response Information
      let u8a_requestResponseInformationType = MqttDataTypes.oneByte(0x19)
      allData.add(u8a_requestResponseInformationType)
      propertiesLength += u8a_requestResponseInformationType.length

      let u8a_requestResponseInformation = MqttDataTypes.oneByte(this.requestResponseInformation)
      allData.add(u8a_requestResponseInformation)
      propertiesLength += u8a_requestResponseInformation.length

      //3.1.2.11.7 Request Problem Information
      let u8a_requestProblemInformationType = MqttDataTypes.oneByte(0x17)
      allData.add(u8a_requestProblemInformationType)
      propertiesLength += u8a_requestProblemInformationType.length

      let u8a_requestProblemInformation = MqttDataTypes.oneByte(this.requestProblemInformation)
      allData.add(u8a_requestProblemInformation)
      propertiesLength += u8a_requestProblemInformation.length

      //3.1.2.11.8 User Property
      if(this.userProperties && this.userProperties.length > 0){
         //3.3.2.3.7 User Property 【UTF-8 String Pair】
         this.userProperties.forEach( (value, key)=>{
            let a8u_userPropertyType = MqttDataTypes.oneByte(0x26)
            allData.add(a8u_userPropertyType)
            propertiesLength += a8u_userPropertyType.length

            let a8u_userProperty = MqttDataTypes.utf8StringPair(key, value)
            allData.add(a8u_userProperty)
            propertiesLength += a8u_userProperty.length
         })
      }

      //3.1.2.11.9 Authentication Method
      if(this.authenticationMethod && this.authenticationMethod.length > 0){
         let u8a_authenticatinMethodType = MqttDataTypes.oneByte(0x15)
         allData.add(u8a_authenticatinMethodType)
         propertiesLength += u8a_authenticatinMethodType.length

         let u8a_authenticatinMethod = MqttDataTypes.utf8String(this.authenticationMethod)
         allData.add(u8a_authenticatinMethod)
         propertiesLength += u8a_authenticatinMethod.length
      }

      //3.1.2.11.10 Authentication Data
      if(this.authenticationData && this.authenticationData.length > 0){
         let u8a_authenticatinDataType = MqttDataTypes.oneByte(0x16)
         allData.add(u8a_authenticatinDataType)
         propertiesLength += u8a_authenticatinDataType.length

         let targetString: string = this.authenticationData
         let textEncoder = new util.TextEncoder()
         let binaryArray = textEncoder.encodeInto(targetString);

         let u8a_authenticatinData = MqttDataTypes.binaryData(binaryArray)
         allData.add(u8a_authenticatinData)
         propertiesLength += u8a_authenticatinData.length
      }

      //3.1.2.11.1 Property Length
      let u8a_propertylength = MqttDataTypes.encodeVariableByteInteger(propertiesLength)
      allData.insert(u8a_propertylength, insertStartIndex)

      remainLength += (u8a_propertylength.length  + propertiesLength)

      //3.1.3 CONNECT Payload
      //3.1.3.1 Client Identifier (ClientID)
      if(this.clientIdentifier == null || this.clientIdentifier.length == 0){
         this.clientIdentifier = "MQTT-" + new Date().getTime() + '-' + Math.random()
      }
      let u8a_clientidentifier = MqttDataTypes.utf8String(this.clientIdentifier)
      allData.add(u8a_clientidentifier)
      remainLength += u8a_clientidentifier.length

      //3.1.3.2 Will Properties
      if(willFlag == 1){
         let willPropertiesLength: number = 0
         let willPropertiesIndex: number = allData.length

         //3.1.3.2.2 Will Delay Interval
         //seconds
         let u8a_willDelayIntervalType = MqttDataTypes.oneByte(0x18)
         allData.add(u8a_willDelayIntervalType)
         willPropertiesLength += u8a_willDelayIntervalType.length

         let u8a_willDelayInterval = MqttDataTypes.fourByte(this.willDelayInterval)
         allData.add(u8a_willDelayInterval)
         willPropertiesLength += u8a_willDelayInterval.length

         //3.1.3.2.3 Payload Format Indicator
         let u8a_payloadformatIndicatorType = MqttDataTypes.oneByte(0x18)
         allData.add(u8a_payloadformatIndicatorType)
         willPropertiesLength += u8a_payloadformatIndicatorType.length

         let u8a_payloadformatIndicator = MqttDataTypes.fourByte(this.payloadFormatIndicator)
         allData.add(u8a_payloadformatIndicator)
         willPropertiesLength += u8a_payloadformatIndicator.length

         //3.1.3.2.4 Message Expiry Interval
         let u8a_messageExpiryIntervalType = MqttDataTypes.oneByte(0x02)
         allData.add(u8a_messageExpiryIntervalType)
         willPropertiesLength += u8a_messageExpiryIntervalType.length

         let u8a_messageExpiryInterval = MqttDataTypes.fourByte(this.messageExpiryInterval)
         allData.add(u8a_messageExpiryInterval)
         willPropertiesLength += u8a_messageExpiryInterval.length

         //3.1.3.2.5 Content Type
         let u8a_contentType = MqttDataTypes.oneByte(0x03)
         allData.add(u8a_contentType)
         willPropertiesLength += u8a_contentType.length

         let u8a_content = MqttDataTypes.utf8String(this.contentType)
         allData.add(u8a_content)
         willPropertiesLength += u8a_content.length

         //3.1.3.2.6 Response Topic
         let u8a_responseTopicType = MqttDataTypes.oneByte(0x08)
         allData.add(u8a_responseTopicType)
         willPropertiesLength += u8a_responseTopicType.length

         let u8a_responseTopic = MqttDataTypes.utf8String(this.responseTopic)
         allData.add(u8a_responseTopic)
         willPropertiesLength += u8a_responseTopic.length

         //3.1.3.2.7 Correlation Data
         let u8a_correlationDataType = MqttDataTypes.oneByte(0x09)
         allData.add(u8a_correlationDataType)
         willPropertiesLength += u8a_correlationDataType.length

         let targetString: string = this.correlationData
         let textEncoder = new util.TextEncoder()
         let binaryArray = textEncoder.encodeInto(targetString);

         let u8a_correlationData = MqttDataTypes.binaryData(binaryArray)
         allData.add(u8a_correlationData)
         willPropertiesLength += u8a_correlationData.length

         //3.1.3.2.8 User Property
         if(this.willUserProperties && this.willUserProperties.length > 0){
            //3.3.2.3.7 User Property 【UTF-8 String Pair】
            this.willUserProperties.forEach( (value, key)=>{
               let a8u_userPropertyType = MqttDataTypes.oneByte(0x26)
               allData.add(a8u_userPropertyType)
               willPropertiesLength += a8u_userPropertyType.length

               let a8u_userProperty = MqttDataTypes.utf8StringPair(key, value)
               allData.add(a8u_userProperty)
               willPropertiesLength += a8u_userProperty.length
            })
         }

         //3.1.3.2.1 Property Length
         let u8a_propertylength = MqttDataTypes.encodeVariableByteInteger(willPropertiesLength)
         allData.insert(u8a_propertylength, willPropertiesIndex)

         remainLength += (u8a_propertylength.length  + willPropertiesLength)

      }

      //3.1.3.3 Will Topic
      if(willFlag == 1){
         let u8a_willTopic = MqttDataTypes.utf8String(this.willTopic)
         allData.add(u8a_willTopic)
         remainLength += u8a_willTopic.length
      }

      //3.1.3.4 Will Payload
      if(willFlag == 1){
         let targetString: string = this.willPayload
         let textEncoder = new util.TextEncoder()
         let binaryArray = textEncoder.encodeInto(targetString);

         let u8a_willPayload = MqttDataTypes.binaryData(binaryArray)
         allData.add(u8a_willPayload)
         remainLength += u8a_willPayload.length
      }

      //3.1.3.5 User Name
      if(willFlag == 1){
         if(((this.connectFlag&0b10000000) >> 7) == 1){
            let u8a_willTopic = MqttDataTypes.utf8String(this.userName)
            allData.add(u8a_willTopic)
            remainLength += u8a_willTopic.length
         }
      }

      //3.1.3.6 Password
      if(willFlag == 1){
         if(((this.connectFlag&0b01000000) >> 6) == 1){
            let targetString: string = this.passWord
            let textEncoder = new util.TextEncoder()
            let binaryArray = textEncoder.encodeInto(targetString);

            let u8a_willPayload = MqttDataTypes.binaryData(binaryArray)
            allData.add(u8a_willPayload)
            remainLength += u8a_willPayload.length
         }
      }

      //3.1.1 CONNECT Fixed Header - 包剩余长度
      let u8a_remainlength = MqttDataTypes.encodeVariableByteInteger(remainLength)
      allData.insert(u8a_remainlength, 1)

      //合并数据
      let allUint8Array = new Uint8Array(1 + u8a_remainlength.length + remainLength)

      let allUint8ArrayIndex: number = 0

      allData.forEach((element: Uint8Array)=>{
           element.forEach( (value) => {
              allUint8Array[allUint8ArrayIndex++] = value
           })
      })

      return allUint8Array

   }

}

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鸿蒙---作为国家主力推送的国产操作系统。部分的高校已经取消了安卓课程，从而开设鸿蒙课程；企业纷纷跟进启动了鸿蒙研发。

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