Learn Tai Chi Maker - mqtt (VI) esp8266 releases mqtt message

Video link ：https://www.bilibili.com/video/BV1Xy4y1z7Mm/?spm_id_from=autoNext&vd_source=b91967c499b23106586d7aa35af46413

The data link ：http://www.taichi-maker.com/homepage/esp8266-nodemcu-iot/iot-tuttorial/mqtt-tutorial/esp8266-publish-mqtt/

ESP8266 towards MQTT Server publishing information

/**********************************************************************  Project name /Project :  Zero basic introduction to the Internet of things   Program name /Program name : publish_ranye_url  The team /Team :  Taiji maker team  / Taichi-Maker (www.taichi-maker.com)  author /Author : CYNO Shuo   date /Date（YYYYMMDD） : 20200813  Purpose of procedure /Purpose :  The purpose of this program is to demonstrate how to use PubSubClient Library usage ESP8266 towards MQTT Server publishing information . -----------------------------------------------------------------------  This sample program is made by Taiji maker team 《 Zero basic introduction to the Internet of things 》 Sample program in .  This tutorial is designed and produced by friends who are interested in the development of the Internet of things . For more information about this tutorial , Please refer to the following pages ： http://www.taichi-maker.com/homepage/esp8266-nodemcu-iot/iot-c/esp8266-nodemcu-web-client/http-request/ ***********************************************************************/
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Ticker.h>
 
//  Set up wifi Access information ( Please according to your WiFi Modify the information )
const char* ssid = "taichi-maker";
const char* password = "12345678";
const char* mqttServer = "test.ranye-iot.net";
 
//  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/
 
Ticker ticker;
WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);
 
int count;    // Ticker Variable for counting 
 
void setup() {
    
  Serial.begin(9600);
  
  // 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);
 
  //  Connect MQTT The server 
  connectMQTTServer();
 
  // Ticker Timing object 
  ticker.attach(1, tickerCount);  
}
 
void loop() {
     
  if (mqttClient.connected()) {
     //  If the development board successfully connects to the server 
    //  every other 3 One message per second 
    if (count >= 3){
    
      pubMQTTmsg();
      count = 0;
    }    
    //  Keep your heart beating 
    mqttClient.loop();
  } else {
                      //  If the development board fails to connect to the server 
    connectMQTTServer();    //  Then try to connect to the server 
  }
}
 
void tickerCount(){
    
  count++;
}
 
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);
  } else {
    
    Serial.print("MQTT Server Connect Failed. Client State:");
    Serial.println(mqttClient.state());
    delay(3000);
  }   
}
 
//  Publish the information 
void pubMQTTmsg(){
    
  static int value; //  The client publishes information in numbers 
 
  //  Create a publishing theme . The title of the topic is Taichi-Maker- The prefix , The device is added later MAC Address .
  //  This is done to ensure that different users MQTT When information is released ,ESP8266 Client names vary ,
  String topicString = "Taichi-Maker-Pub-" + WiFi.macAddress();
  char publishTopic[topicString.length() + 1];  
  strcpy(publishTopic, topicString.c_str());
 
  //  Establish and release information . The information content is in Hello World As the starting point , Add the number of releases later .
  String messageString = "Hello World " + String(value++); 
  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."); 
  }
}
 
// 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(""); 
}

See how it works , as follows ：

In the example above ,ESP8266 Every interval 3 Seconds to ( Taichi-Maker- The prefix , The device is added later MAC Address , namely Taichi-Maker-Pub-EC:FA:BC:40:6F:5B ) The subject of a news release , The message is （ Hello World As the starting point , Add the number of releases later ）.

We copied the topic to MQTT.fx In this software , Then subscribe to .

Next, I will explain the contents of the program carefully .

//  Publish the information 
void pubMQTTmsg(){
    
  static int value; //  The client publishes information in numbers 
 
  //  Create a publishing theme . The title of the topic is Taichi-Maker- The prefix , The device is added later MAC Address .
  //  This is done to ensure that different users MQTT When information is released ,ESP8266 Client names vary ,
  String topicString = "Taichi-Maker-Pub-" + WiFi.macAddress();
  char publishTopic[topicString.length() + 1];  
  strcpy(publishTopic, topicString.c_str());
 
  //  Establish and release information . The information content is in Hello World As the starting point , Add the number of releases later .
  String messageString = "Hello World " + String(value++); 
  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."); 
  }
}

1、 Why convert to a character array ？

It's because it's executing mqttClient.publish When this function , The parameters it can accept must be of character array type . After execution mqttClient.publish There will be a return value after , Successfully returns 1 .

2、 After successfully publishing the message , And maintain the heartbeat mechanism .

 //  Keep your heart beating 
 mqttClient.loop();