I am trying to establish communication between ESP32 and Node-Red, where as ESP32 will be in remote location, that’s why the use of LoraWan comes into the scenario. I am using PubSubClient library to use MQTT but I am getting some errors related to constructor which is shown below.

#include <Arduino.h>
#include <LoRa.h>
#include <PubSubClient.h>

const int pin_ss = 5;
const int pin_rst = 14;
const int pin_dio0 = 26;
const char* mqttServer = “192.168.137.216”;
const int mqttPort = 1883;
const char* mqttUser = “pi”;
const char* mqttPassword = “Admin123”;
const char* loraTopic = “Test”;

void callback(char* topic, byte* payload, unsigned int length)
{
  Serial.print(“Message arrived [“);
  Serial.print(topic);
  Serial.print(“] “);
  for (int i = 0; i < length; i++)
  {
  Serial.print((char)payload[i]);
  }
  Serial.println();
}
PubSubClient mqttClient(mqttServer, mqttPort);

//PubSubClient mqttClient(loraTopic, mqttServer, mqttPort, callback, mqttUser, mqttPassword);
mqttClient.connect(loraTopic, mqttUser, mqttPassword);

void setup()
{
  Serial.begin(115200);
// initialize LoRa module
  LoRa.setPins(pin_ss, pin_rst, pin_dio0);
  if (!LoRa.begin(866E6)) {
    Serial.println(“Starting LoRa failed!”);
    while (1);
  }
// connect to MQTT broker
while (!mqttClient.connect())
{
delay(1000);
Serial.println(“Connecting to MQTT…”);
}
Serial.println(“Connected to MQTT”);
mqttClient.subscribe(loraTopic);
}
void loop() {
mqttClient.loop();
// send message to the topic
String message = “Hello from ESP32”;
mqttClient.publish(loraTopic, message.c_str());
delay(1000);
}

 
ERROR : Compilation error: no matching function for call to ‘PubSubClient::PubSubClient(const char*&, const int&)’