Learn Tai Chi Maker - mqtt (VIII) esp8266 subscribe to mqtt topic

Video link ：https://www.bilibili.com/video/BV1Wz4y1k7Fs/?spm_id_from=333.788.recommend_more_video.-1&vd_source=b91967c499b23106586d7aa35af46413

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

1、 Subscribe to a single topic

/**********************************************************************  Project name /Project :  Zero basic introduction to the Internet of things   Program name /Program name : subscribe_ranye_url  The team /Team :  Taiji maker team  / Taichi-Maker (www.taichi-maker.com)  author /Author : CYNO Shuo   date /Date（YYYYMMDD） : 20200708  Purpose of procedure /Purpose :  The purpose of this program is to demonstrate how to use PubSubClient Library usage ESP8266 towards MQTT Server subscription 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>
 
//  Set up wifi Access information ( Please according to your WiFi Modify the information )
const char* ssid = "FAST_153C80";
const char* password = "123456798";
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/
 
WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);
 
void setup() {
    
  pinMode(LED_BUILTIN, OUTPUT);     //  Set up on the board LED Pin is output mode 
  digitalWrite(LED_BUILTIN, HIGH);  //  Turn it on and off the board LED
  Serial.begin(9600);               //  Start serial communication 
  
  // 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);
  //  Set up MQTT Subscription callback function 
  mqttClient.setCallback(receiveCallback);
 
  //  Connect MQTT The server 
  connectMQTTserver();
}
 
void loop() {
    
  if (mqttClient.connected()) {
     //  If the development board successfully connects to the server 
    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);
 
  if ((char)payload[0] == '1') {
         //  If you receive a message with “1” For the beginning 
    digitalWrite(BUILTIN_LED, LOW);  //  Then light up LED.
    Serial.println("LED ON");
  } else {
                               
    digitalWrite(BUILTIN_LED, HIGH); //  Otherwise, it goes out LED.
    Serial.println("LED OFF");
  }
}
 
//  Subscribe to specific topics 
void subscribeTopic(){
    
 
  //  Create a subscription topic . The title of the topic is Taichi-Maker-Sub The prefix , The device is added later MAC Address .
  //  This is to make sure that different devices use the same MQTT When the server tests the message subscription , The topic names you subscribe to are different 
  String topicString = "Taichi-Maker-Sub-" + WiFi.macAddress();
  char subTopic[topicString.length() + 1];  
  strcpy(subTopic, topicString.c_str());
  
  //  The serial port monitor outputs whether the topic is successfully subscribed and the name of the subscription topic 
  if(mqttClient.subscribe(subTopic)){
    
    Serial.println("Subscrib Topic:");
    Serial.println(subTopic);
  } else {
    
    Serial.print("Subscribe Fail...");
  }  
}
 
// 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(""); 
}

The program runs as follows ,

Let's try again MQTT.fx This software provides Taichi-Maker-Sub-EC:FA:BC:40:6F:5B This topic publishes information , At the same time, observe the output of the serial port monitor .

When LED ON when ,ESP8266 On board LED Also lit .

below , To explain the key points of the program .

  //  Set up MQTT Subscription callback function 
  mqttClient.setCallback(receiveCallback);

Here ESP8266 The function of the development board is to subscribe MQTT The theme , It is subscribing MQTT After the theme , Whenever you receive this topic message , He will call a callback function receiveCallback , To process the received information .

2、 Subscribe to specific topics

//  The serial port monitor outputs whether the topic is successfully subscribed and the name of the subscription topic 
  if(mqttClient.subscribe(subTopic)){
    
    Serial.println("Subscrib Topic:");
    Serial.println(subTopic);
  } else {
    
    Serial.print("Subscribe Fail...");
  }  

mqttClient.subscribe(subTopic) Will try to subscribe to a topic , The theme is called “Taichi-Maker-Sub-” + WiFi.macAddress(),
If the subscription is successful, it will return 1 .

3、 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);
 
  if ((char)payload[0] == '1') {
         //  If you receive a message with “1” For the beginning 
    digitalWrite(BUILTIN_LED, LOW);  //  Then light up LED.
    Serial.println("LED ON");
  } else {
                               
    digitalWrite(BUILTIN_LED, HIGH); //  Otherwise, it goes out LED.
    Serial.println("LED OFF");
  }
}

Notice the three parameters , The three parameters are fixed format .

topic It's the theme name
payload Is the content of specific information , It's an array type
length Is the length of the specific information

2、 Subscribe to multiple topics

/**********************************************************************  Project name /Project :  Zero basic introduction to the Internet of things   Program name /Program name : subscribe_multitopic_ranye_url  The team /Team :  Taiji maker team  / Taichi-Maker (www.taichi-maker.com)  author /Author : CYNO Shuo   date /Date（YYYYMMDD） : 20201125  Purpose of procedure /Purpose :  The purpose of this program is to demonstrate how to use PubSubClient Library usage ESP8266 towards MQTT The server subscribes to multiple topics  -----------------------------------------------------------------------  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>
 
//  Set up wifi Access information ( Please according to your WiFi Modify the information )
const char* ssid = "FAST_153C80";
const char* password = "123456798";
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/
 
WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);
 
void setup() {
    
  pinMode(LED_BUILTIN, OUTPUT);     //  Set up on the board LED Pin is output mode 
  digitalWrite(LED_BUILTIN, HIGH);  //  Turn it on and off the board LED
  Serial.begin(9600);               //  Start serial communication 
  
  // 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 
    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);
 
  if ((char)payload[0] == '1') {
         //  If you receive a message with “1” For the beginning 
    digitalWrite(BUILTIN_LED, LOW);  //  Then light up LED.
  } else {
                               
    digitalWrite(BUILTIN_LED, HIGH); //  Otherwise, it goes out LED.
  }
}
 
//  Subscribe to specific topics 
void subscribeTopic(){
    
 
  //  Create a subscription topic 1. The title of the topic is Taichi-Maker-Sub The prefix , The device is added later MAC Address .
  //  This is to make sure that different devices use the same MQTT When the server tests the message subscription , The topic names you subscribe to are different 
  String topicString = "Taichi-Maker-Sub-" + WiFi.macAddress();
  char subTopic[topicString.length() + 1];  
  strcpy(subTopic, topicString.c_str());
  
  //  Create a subscription topic 2
  String topicString2 = "Taichi-Maker-Sub2-" + WiFi.macAddress();
  char subTopic2[topicString2.length() + 1];  
  strcpy(subTopic2, topicString2.c_str());
  
  //  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(subTopic)){
    
    Serial.println("Subscrib Topic:");
    Serial.println(subTopic);
  } 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 
  if(mqttClient.subscribe(subTopic2)){
    
    Serial.println("Subscrib Topic:");
    Serial.println(subTopic2);
  } else {
    
    Serial.print("Subscribe Fail...");
  }    
}
 
// 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(""); 
}

The running code is as follows ,

Let's try again MQTT.fx This software is directed to Taichi-Maker-Sub-EC:FA:BC:40:6F:5B and Taichi-Maker-Sub2-EC:FA:BC:40:6F:5B These two topics publish information , At the same time, observe the output of the serial port monitor .

No matter which topic you post on , As long as the first character of the message is 1 , Then light up the onboard LED .

3、 Subscribe to topics using single level wildcards

/**********************************************************************  Project name /Project :  Zero basic introduction to the Internet of things   Program name /Program name : subscribe_single_level_wildcard_ranye  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 procedure is to demonstrate ESP8266 Unipolar wildcard when subscribing to information + application . -----------------------------------------------------------------------  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>
 
//  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/
 
WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);
 
void setup() {
    
  pinMode(LED_BUILTIN, OUTPUT);     //  Set up on the board LED Pin is output mode 
  digitalWrite(LED_BUILTIN, HIGH);  //  Turn it on and off the board LED
  Serial.begin(9600);               //  Start serial communication 
  
  // 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 
    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);
 
  if ((char)payload[0] == '1') {
         //  If you receive a message with “1” For the beginning 
    digitalWrite(BUILTIN_LED, LOW);  //  Then light up LED.
  } else {
                               
    digitalWrite(BUILTIN_LED, HIGH); //  Otherwise, it goes out LED.
  }
}
 
//  Subscribe to specific topics 
void subscribeTopic(){
    
 
  //  Create a subscription topic . The title of the topic is Taichi-Maker-Sub The prefix , The device is added later MAC Address .
  //  This is to make sure that different devices use the same MQTT When the server tests the message subscription , The topic names you subscribe to are different 
  String topicString = "Taichi-Maker-Sub-" + WiFi.macAddress()+"/+/data";
  char subTopic[topicString.length() + 1];  
  strcpy(subTopic, topicString.c_str());
  
  //  The serial port monitor outputs whether the topic is successfully subscribed and the name of the subscription topic 
  if(mqttClient.subscribe(subTopic)){
    
    Serial.println("Subscrib Topic:");
    Serial.println(subTopic);
  } else {
    
    Serial.print("Subscribe Fail...");
  }  
}
 
// 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(""); 
}

It is similar to the first program .

4、 Use multi-level wildcards to subscribe to topics

/**********************************************************************  Project name /Project :  Zero basic introduction to the Internet of things   Program name /Program name : subscribe_multi_level_wildcard_ranye  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 procedure is to demonstrate ESP8266 Multipole wildcard when subscribing to information # application . -----------------------------------------------------------------------  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>
 
//  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/
 
WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);
 
void setup() {
    
  pinMode(LED_BUILTIN, OUTPUT);     //  Set up on the board LED Pin is output mode 
  digitalWrite(LED_BUILTIN, HIGH);  //  Turn it on and off the board LED
  Serial.begin(9600);               //  Start serial communication 
  
  // 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 
    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);
 
  if ((char)payload[0] == '1') {
         //  If you receive a message with “1” For the beginning 
    digitalWrite(BUILTIN_LED, LOW);  //  Then light up LED.
  } else {
                               
    digitalWrite(BUILTIN_LED, HIGH); //  Otherwise, it goes out LED.
  }
}
 
//  Subscribe to specific topics 
void subscribeTopic(){
    
 
  //  Create a subscription topic . The title of the topic is Taichi-Maker-Sub The prefix , The device is added later MAC Address .
  //  This is to make sure that different devices use the same MQTT When the server tests the message subscription , The topic names you subscribe to are different 
  String topicString = "Taichi-Maker-Sub-" + WiFi.macAddress()+"/sensor/#";
  char subTopic[topicString.length() + 1];  
  strcpy(subTopic, topicString.c_str());
  
  //  The serial port monitor outputs whether the topic is successfully subscribed and the name of the subscription topic 
  if(mqttClient.subscribe(subTopic)){
    
    Serial.println("Subscrib Topic:");
    Serial.println(subTopic);
  } else {
    
    Serial.print("Subscribe Fail...");
  }  
}
 
// 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(""); 
}

It is similar to the first program .