MQTT callback do not work

Projects Programming
1

Hello,

I'm using an ESP8266 that connects wifi and to MQTT server.
the code connects nicely to wifi and to MQTT, it publishes the topic but the callback function is not triggered when I publish the subscribed topic from elsewhere (I use MQTT Explorer for win)

here the code.. I think it is the simplest possible but maybe I miss something...

**
#include <ESP8266WiFi.h>
#include <PubSubClient.h>



const char* ssid = "-------"; // Enter your WiFi name
const char* password =  "--------------"; // Enter WiFi password
const char* mqttServer = "192.168.0.15";
const int mqttPort = 1883;
const char* mqttUser = "";
const char* mqttPassword = "";
 
WiFiClient espClient;
PubSubClient client(espClient);


void callback(char* topic, byte* payload, unsigned int length) {
 
  Serial.print("Message arrived in topic: ");
  Serial.println(topic);
 
  Serial.print("Message:");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
 
  Serial.println();
  Serial.println("-----------------------");
 
}


void setup() {
  Serial.begin(9600);
  WiFi.begin(ssid, password);
 
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi..");
  }
  Serial.println("Connected to the WiFi network");
 
  client.setServer(mqttServer, mqttPort);
  client.setCallback(callback);
 
  while (!client.connected()) {
    Serial.println("Connecting to MQTT...");
 
    if (client.connect("ESP8266Client", mqttUser, mqttPassword )) {
 
      Serial.println("connected");  
 
    } else {
 
      Serial.print("failed with state ");
      Serial.print(client.state());
      delay(2000);
 
    }
  
  client.publish("esp/test", "hello"); //Topic name
  client.subscribe("esp/testb");
  }
}





void loop() {
  client.loop();
}**

thanks
Andrea

2

are you sure you modified the "esp/testb" topic ? (not the one you posted to "esp/test")

can you change the loop to

void loop()
{
  if (!client.connected())  reconnect();
  client.loop();
}

can you share exactly what you see in the Serial monitor?

3

hello,
thanks, I added the reconnect and now it works. thank you so much, very much appreciated!!


#include <ESP8266WiFi.h>
#include <PubSubClient.h>



const char* ssid = "--------"; // Enter your WiFi name
const char* password =  "--------------------"; // Enter WiFi password
const char* mqttServer = "192.168.0.15";
const int mqttPort = 1883;
const char* mqttUser = "";
const char* mqttPassword = "";
 
WiFiClient espClient;
PubSubClient client(espClient);


void callback(char* topic, byte* payload, unsigned int length) {
 
  Serial.print("Message arrived in topic: ");
  Serial.println(topic);
 
  Serial.print("Message:");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
 
  Serial.println();
  Serial.println("-----------------------");
 
}


void setup() {
  Serial.begin(9600);
  WiFi.begin(ssid, password);
 
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi..");
  }
  Serial.println("Connected to the WiFi network");
 
  client.setServer(mqttServer, mqttPort);
  client.setCallback(callback);
 
  while (!client.connected()) {
    Serial.println("Connecting to MQTT...");
 
    if (client.connect("ESP8266Client", mqttUser, mqttPassword )) {
 
      Serial.println("connected");  
 
    } else {
 
      Serial.print("failed with state ");
      Serial.print(client.state());
      delay(2000);
 
    }
  
  client.publish("esp/test", "hello"); //Topic name
  client.subscribe("esp/testb");
  }
}

// ///////////////reconnect////////////////////////////
void reconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    if (client.connect("ESP8266Client_Monitor1", mqttUser, mqttPassword)) {
      Serial.println("connected");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}


void loop() {
  if (!client.connected())  reconnect();
  client.loop();
}
4

great have fun!