NodeMCU学习（十一）--MQTT的订阅与发布

电玩女神 2022-10-26 03:46 360阅读 0赞

NodeMCU实现订阅和发布主题。

## 1、要点扫盲 ##

### 1.1  MQTT ###

[《MQTT协议--MQTT协议简介及原理》 ][MQTT_--MQTT]

[《MQTT协议--MQTT协议解析》][MQTT_--MQTT 1]

### 1.2  OneNET ###

[《NodeMCU学习（十）--发送数据到OneNET物联网平台》][NodeMCU_--_OneNET]

[《NodeMCU学习（九）--连接OneNET物联网平台》][NodeMCU_--_OneNET 1]

[《OneNET物联网平台介绍》][OneNET]

[OneNET物联网平台][OneNET 1]

[《设备终端接入协议-MQTT》][-MQTT]

## 2、主要API ##

### 2.1  WiFi ###

（1）wifi.setmode()

（2）wifi.sta.config()

（3）wifi.sta.connect()

关于API的使用方法，可以参考博客[《NodeMCU学习（六）--WiFi》][NodeMCU_--WiFi]，也可以参考[官网][Link 1]对API的说明。

### 2.2  MQTT ###

（1）[mqtt.Client()][mqtt.Client]

（2）[mqtt.client:connect()][mqtt.client_connect]

（3）[mqtt.client:publish()][mqtt.client_publish]

（5）[mqtt.client:on()][mqtt.client_on]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70][]

（6） [mqtt.client:subscribe()][mqtt.client_subscribe]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 1][]

## 3、OneNET平台接入流程  ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 2][]

## 4、编写Lua脚本 ##

### 4.1  源代码 ###

cfg = {}
    cfg.ssid = "OnePlus6"
    cfg.pwd = "1234567890"
    
    wifi.setmode(wifi.STATIONAP)
    wifi.sta.config(cfg)
    wifi.sta.connect()
    
    DeviceID = "1234567890"
    ProductID = "123456"
    KeepAlive = 20
    AuthoInfo = "123456"
    
    host = "183.230.40.39"
    port = 6002
    
    myClient = mqtt.Client(DeviceID, KeepAlive, ProductID, AuthoInfo)
    
    timer1 = tmr.create()
    timer2 = tmr.create()
    
    function ReConnect()
        if wifi.sta.getip() == nil then
            print("Connect AP,waitting...")
        else
            print("Connected AP ,success!")
            print("IP is:"..wifi.sta.getip())
            timer1:stop()
    
            myClient:connect(host, port, function(client)
                print("Connected OneNET success!")
            end)
    
            myClient:on("connect", function(clinet)
                if(myClient:subscribe("pc_to_mcu_topic",0)) then
                    print("subscribe is success.")
                end
            end)
        
            myClient:on("message", function(client , topic , message)
                print("get a message.\n")
                print(topic..":"..message)
            end) 
            
            timer2:alarm(1000, tmr.ALARM_AUTO, Update_Message)
        end
    end
    
    timer1:alarm(1000,tmr.ALARM_AUTO,ReConnect)
    
    currentSum = 0
    voltageSum = 0        
    function Update_Message()
        info = {}
        info.curr = currentSum
        info.volt = voltageSum
    
        currentSum = currentSum + 1
        voltageSum = voltageSum - 1
        ok,message = pcall(sjson.encode, info)
        print("message:"..message)
    
        header = string.char(3, 0 ,string.len(message))..message
        myClient:publish("$dp", header, 0, 0, function(client)
            print("Publish info success!")
        end)
    
        myClient:publish("led1_topic", "led1", 0, 0, function(client) 
          --print("PUBLISH led SUCCESS!")
        end)
    end

4.2  代码解析

**（1）myClient = mqtt.Client(DeviceID, KeepAlive, ProductID, AuthoInfo)**

DeviceID = "1234567890"--根据自己的设备ID填写  
ProductID = "123456"--根据自己的产品ID填写  
KeepAlive = 20--保持连接的间隔时间，可根据实际需要填写  
AuthoInfo = "123456"--设备对应的鉴权信息

**（2）myClient:connect()**

myClient:connect(host, port, function(client)  
            print("Connected OneNET success!")  
        end)

host：OneNET平台的MQTT协议对应的服务器IP

port：OneNET平台的MQTT协议对应的服务器开放的端口

function(client)（）：连接成功后的回调函数

**（3）ok,message = pcall(sjson.encode, info)**

1）pcall在保护模式（protected mode）下执行函数内容，同时捕获所有的异常和错误。若一切正常，pcall返回true以及“被执行函数”的返回值；否则返回nil和错误信息。

2）把info转换为json键值对；

**（4）header = string.char(3, 0 ,string.len(message))..message**

1）string.char()把数字或字符连接成字符串；

2）header为MQTT协议中的协议头，3表示`MQTT`数据包类型为PUBLISH

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 3][]

**（5）myClient:publish()**

myClient:publish("$dp", header, 0, 0, function(client)  
        print("Publish info success!")  
    end)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 4][]

topic:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 5][]

Payload：包含真正的数据点内容；

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 6][]

function(client)（）为发送成功后的回调函数；

**（6）mqtt.client:on()，监听事件**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 7][]

**（7）mqtt.client:subscribe()，订阅主题**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 8][]

## 5、调试 ##

### 5.1  准备工作 ###

（1）需要在平台上创建两个设备；

（2）两个NodeMCU模块，或者用两个MQTT调试软件代替也可以（本人使用一个NodeMCU模块，另一个客户端用调试软件代替）；

（3）MQTT协议调试软件，“simulatedevice\_v1.0.7.exe”，该软件可以在OneNET平台上获取；

### 5.2  试验目的 ###

通过OneNET平台，实现两个不同网络的客户端进行数据交互。

### 5.3  订阅主题 ###

NodeMCU订阅主题，MQTT调试软件发布主题。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 9][]

### 5.4  发布主题 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 10][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p3Yl81NzgyMDkxNjA_size_16_color_FFFFFF_t_70 11][]

## 6、视频教程 ##

[【NodeMCU/ESP8266\_LUA开发】全网最新，全部开源，教你如何用手机远程控制][NodeMCU_ESP8266_LUA]

[MQTT_--MQTT]: https://blog.csdn.net/zwb_578209160/article/details/113365191
[MQTT_--MQTT 1]: https://blog.csdn.net/zwb_578209160/article/details/113365620
[NodeMCU_--_OneNET]: https://blog.csdn.net/zwb_578209160/article/details/113518104
[NodeMCU_--_OneNET 1]: https://blog.csdn.net/zwb_578209160/article/details/113414264
[OneNET]: https://blog.csdn.net/zwb_578209160/article/details/113413667
[OneNET 1]: https://open.iot.10086.cn/
[-MQTT]: https://download.csdn.net/download/zwb_578209160/14983475
[NodeMCU_--WiFi]: https://blog.csdn.net/zwb_578209160/article/details/113315330
[Link 1]: https://nodemcu.readthedocs.io/en/release/modules/wifi/#wifisetmode
[mqtt.Client]: https://nodemcu.readthedocs.io/en/release/modules/mqtt/#mqttclient
[mqtt.client_connect]: https://nodemcu.readthedocs.io/en/release/modules/mqtt/#mqttclientconnect
[mqtt.client_publish]: https://nodemcu.readthedocs.io/en/release/modules/mqtt/#mqttclientpublish
[mqtt.client_on]: https://nodemcu.readthedocs.io/en/release/modules/mqtt/#mqttclienton
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[mqtt.client_subscribe]: https://nodemcu.readthedocs.io/en/release/modules/mqtt/#mqttclientsubscribe
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[NodeMCU_ESP8266_LUA]: https://www.bilibili.com/video/BV1S7411t7RX