MQTT PubSubClient error on 'callback' function!

Projects Programming
1

Hi,

I have the Arduino version 1.8.0 and the PubSubClient Library version 2.6.0.

When I try this code from here:

//ItKindaWorks - Creative Commons 2016
//github.com/ItKindaWorks
//
//Requires PubSubClient found here: https://github.com/knolleary/pubsubclient
//
//ESP8266 Simple MQTT light controller


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


//EDIT THESE LINES TO MATCH YOUR SETUP
#define MQTT_SERVER "YOUR.MQTT.SERVER.IP"
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";

//LED on ESP8266 GPIO2
const int lightPin = 2;

char* lightTopic = "/test/light1";


WiFiClient wifiClient;
PubSubClient client(MQTT_SERVER, 1883, callback, wifiClient);

void setup() {
	//initialize the light as an output and set to LOW (off)
	pinMode(lightPin, OUTPUT);
	digitalWrite(lightPin, LOW);

	//start the serial line for debugging
	Serial.begin(115200);
	delay(100);


	//start wifi subsystem
	WiFi.begin(ssid, password);
	//attempt to connect to the WIFI network and then connect to the MQTT server
	reconnect();

	//wait a bit before starting the main loop
    	delay(2000);
}



void loop(){

	//reconnect if connection is lost
	if (!client.connected() && WiFi.status() == 3) {reconnect();}

	//maintain MQTT connection
	client.loop();

	//MUST delay to allow ESP8266 WIFI functions to run
	delay(10); 
}


void callback(char* topic, byte* payload, unsigned int length) {

	//convert topic to string to make it easier to work with
	String topicStr = topic; 

	//Print out some debugging info
	Serial.println("Callback update.");
	Serial.print("Topic: ");
	Serial.println(topicStr);

	//turn the light on if the payload is '1' and publish to the MQTT server a confirmation message
	if(payload[0] == '1'){
		digitalWrite(lightPin, HIGH);
		client.publish("/test/confirm", "Light On");

	}

	//turn the light off if the payload is '0' and publish to the MQTT server a confirmation message
	else if (payload[0] == '0'){
		digitalWrite(lightPin, LOW);
		client.publish("/test/confirm", "Light Off");
	}

}


void reconnect() {

	//attempt to connect to the wifi if connection is lost
	if(WiFi.status() != WL_CONNECTED){
		//debug printing
		Serial.print("Connecting to ");
		Serial.println(ssid);

		//loop while we wait for connection
		while (WiFi.status() != WL_CONNECTED) {
			delay(500);
			Serial.print(".");
		}

		//print out some more debug once connected
		Serial.println("");
		Serial.println("WiFi connected");  
		Serial.println("IP address: ");
		Serial.println(WiFi.localIP());
	}

	//make sure we are connected to WIFI before attemping to reconnect to MQTT
	if(WiFi.status() == WL_CONNECTED){
	// Loop until we're reconnected to the MQTT server
		while (!client.connected()) {
			Serial.print("Attempting MQTT connection...");

			// Generate client name based on MAC address and last 8 bits of microsecond counter
			String clientName;
			clientName += "esp8266-";
			uint8_t mac[6];
			WiFi.macAddress(mac);
			clientName += macToStr(mac);

			//if connected, subscribe to the topic(s) we want to be notified about
			if (client.connect((char*) clientName.c_str())) {
				Serial.print("\tMTQQ Connected");
				client.subscribe(lightTopic);
			}

			//otherwise print failed for debugging
			else{Serial.println("\tFailed."); abort();}
		}
	}
}

//generate unique name from MAC addr
String macToStr(const uint8_t* mac){

  String result;

  for (int i = 0; i < 6; ++i) {
    result += String(mac[i], 16);

    if (i < 5){
      result += ':';
    }
  }

  return result;
}

I get the following error while compiling the sketch:

MQTT_v2:25: error: 'callback' was not declared in this scope

 PubSubClient client(MQTT_SERVER, 1883, callback, wifiClient);

                                        ^

exit status 1
'callback' was not declared in this scope

I'm amazed with the inconsistency of the Arduino IDE! :fearful:

Any solution?

Thanks

2

Try moving the function to the top of the sketch?

3

ElCaron:
Try moving the function to the top of the sketch?

I did that, then it gives me another error complaining that the callback's "client.publish" isn't defined!

The author told me this:

That has been an issue with the Arduino ESP8266 plugin. You can fix it by adding this line to the top of the program: void callback(char* topic, byte* payload, unsigned int length);

I haven't tried yet, but it looks like you declare the function in the top and do its code after... Silly I know!

4

If you stopped jamming the curly braces up against statements, and put them on new lines where they belong, it would become perfectly obvious what the problem is.

Where does loop() end? Probably not where you think it does.