Esp32 (based on Arduino) connects the mqtt server of emqx to upload information and command control

Preface : 

EMQX The open source version provides free local LAN mqtt The server , Many operations of the Internet of things can be realized by subscribing to the theme and publishing the information under the theme . What operation ？ Such as dumping the sensor information collected by the device to the local database through subscription . The switch of the equipment is controlled by publishing .

The upload information and command control are based on a client built locally by me as the intermediate hub . The local client opens a web And provides interface access .

Upload information ：

Because I have written a client subscription locally ESP32 The topic of the release information device/date,esp32 Each pair device/date Release a message , The client will dump it to mysql database .

Command control ：

esp32 subscribe esp32/dev/# , Not exactly , there # It can be 1,2,3 representative esp32 The controller dev1,dev2,dev3（ about esp32 disjunctive led The lamp , The motor , Buzzer, etc ）. The control here is the most direct control , In order to achieve indirect control, such as Andrade ,web End control can send parameters through the interface to let the local client publish esp32/dev/# The information under the corresponding topic is controlled by ESP32.

problem ：

1:esp32 Of json Send data and let the client receive .

Reference resources

Arduino-ESP32 Medium Json Construction and analysis _ Xingshuiguagua's blog -CSDN Blog _arduino esp32 json

Add library

#include <ArduinoJson.h>

What is sent is in the form of string json data

StaticJsonDocument<200> sensor_json;
sensor_json["sensor_val"] = hallRead();
sensor_json["sensor_val"] = cnt;
sensor_json["to"] = "starmelon";
String msg;
serializeJson(sensor_json, msg);

2：esp32 Can't connect emqx Of mqtt The server .

Because it is under the LAN ,emqx Under the mqtt The server has its LAN address , This LAN address is emqx Of the host ip Address , If you use a local LAN built by a router and use IP Automatic allocation , You need to change the server address every time , The same is true for connecting mobile phone hotspots .

Default domain name :"broker-cn.emqx.io"  String format

  The problem is coming. , When I use this default domain name as the server address ,esp32 You can really send messages to the set theme , But on my host poho（ A monitoring software ） And the client did not receive the message .

 

Only when I return to my original state , Use LAN address 192.168.43.234,esp32 Can work normally ,poho And the client can also work normally .

Normal message reporting

 

Realization :

 
#include <WiFi.h>
#include <PubSubClient.h>
#include <Ticker.h>
#include <ArduinoJson.h>

StaticJsonDocument<200> sensor_json;
 String realmsg="";
int LED=2;
//  Set up wifi Access information ( Please according to your WiFi Modify the information )
const char* ssid = "realme";
const char* password = "12345678";
const char* mqttServer = "192.168.43.246";// This machine ip Address 
// Published message field 
typedef struct {
  int msg1;
  int msg2;
  int msg3;
}msg;
int count=0;// Publish message interval 
//  As above MQTT The server cannot connect normally , Please go to the following page to find a solution 
// http://www.taichi-maker.com/public-mqtt-broker/
//------------------ Global variable definition -----------------
msg mymsg={123,45,6};// Define the message structure 
 
Ticker ticker;
WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);
//------------------ Global variable definition -----------------
void tickerCount(){//Ticker Callback function 
  count++;
  // The test data 
sensor_json["msg1"] = 12;
sensor_json["msg2"] =21;
sensor_json["msg3"] = 98;
serializeJson(sensor_json, realmsg);
}

void pubmsg( const String &topicString, const  String &messageString){
  char publishTopic[topicString.length() + 1];  
  strcpy(publishTopic, topicString.c_str());
  char publishMsg[messageString.length() + 1];   
  strcpy(publishMsg, messageString.c_str());
  
  //  Realization ESP8266 Post information to the subject 
  if(mqttClient.publish(publishTopic, publishMsg)){
    Serial.println("Publish Topic:");Serial.println(publishTopic);
    Serial.println("Publish message:");Serial.println(publishMsg);    
  } else {
    Serial.println("Message Publish Failed."); 
  }
}
void setup() {
  pinMode(LED, OUTPUT);     //  Set up on the board LED Pin is output mode 
  digitalWrite(LED, LOW);  //  Turn it on and off the board LED
  Serial.begin(9600);               //  Start serial communication 

  // Ticker Timing object 
  ticker.attach(2, tickerCount); // every 2s Call its callback function 
  
  // Set up ESP8266 The working mode is wireless terminal mode 
  WiFi.mode(WIFI_STA);
  
  //  Connect WiFi
  connectWifi();
  
  //  Set up MQTT Server and port number 
  mqttClient.setServer(mqttServer, 1883);
  mqttClient.setCallback(receiveCallback);
 
  //  Connect MQTT The server 
  connectMQTTserver();
}

void loop() {
  if (mqttClient.connected()) { //  If the development board successfully connects to the server 
   if (count >= 2){
      pubmsg("device/date",realmsg);
      realmsg="";
      count = 0;
    }
    
    mqttClient.loop();          //  Process information and heartbeat    
  } else {                      //  If the development board fails to connect to the server 
    connectMQTTserver();        //  Then try to connect to the server 
  }
}

//  Connect MQTT Server and subscribe to information 
void connectMQTTserver(){
  //  according to ESP8266 Of MAC Address generation client ID（ Avoid contact with other ESP8266 The client of ID The nuptial ）
  String clientId = "esp8266-" + WiFi.macAddress();
 
  //  Connect MQTT The server 
  if (mqttClient.connect(clientId.c_str())) { 
    Serial.println("MQTT Server Connected.");
    Serial.println("Server Address:");
    Serial.println(mqttServer);
    Serial.println("ClientId: ");
    Serial.println(clientId);
    subscribeTopic(); //  Subscribe to specific topics 
  } else {
    Serial.print("MQTT Server Connect Failed. Client State:");
    Serial.println(mqttClient.state());
    delay(5000);
  }   
}
//  Callback function after receiving information 
void receiveCallback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message Received [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println("");
  Serial.print("Message Length(Bytes) ");
  Serial.println(length);
  int temp=0;
  while(*topic){
    temp++;
    topic++;
  }
  Serial.println(" Theme length :");
  Serial.println(temp);
  if(temp>11){
    if((char)topic[11]=='1'){
          if ((char)payload[0] == 'O' && (char)payload[1] == 'F') {     //  If you receive a message with “1” For the beginning 
            digitalWrite(LED, LOW);  //  Then light up LED.
          } else {                           
            digitalWrite(LED, HIGH); //  Otherwise, it goes out LED.
          }
    }
  }
}
 
//  Subscribe to specific topics 
void subscribeTopic(){
 
 
  
  //  Output whether the topic has been successfully subscribed through the serial port monitor 1 And the topics you subscribe to 1 name 
  if(mqttClient.subscribe("device/dev/#")){
    Serial.println("Subscrib Topic:");
    Serial.println("device/action");
  } else {
    Serial.print("Subscribe Fail...");
  }  
 
  //  Output whether the topic has been successfully subscribed through the serial port monitor 2 And the topics you subscribe to 2 name 
     
}
 
// ESP8266 Connect wifi
void connectWifi(){
 
  WiFi.begin(ssid, password);
 
  // wait for WiFi Connect , Output success information after successful connection 
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi Connected!");  
  Serial.println(""); 
}

effect :

  stay poho The control information can be released on the control board LED The lamp .

 

Reference resources :

Zero basic introduction to the Internet of things – MQTT The basic chapter – Catalog – Taiji maker (taichi-maker.com)