mqtt error code RC = -1 connecting while esp32 to aws - amazon-web-services

Question

I am going to establish a mqtt connection to aws. DHT senstor reading must be sent from esp32 to aws. How can I fix the error RC = -1 when connecting esp32 to aws. I receive this error in serial monitor :
Attempting MQTT connection...failed, rc=-1 try again in 5 seconds
What can be the reaon?
My code is as follows:
#include "SPIFFS.h"
#include <WiFiClientSecure.h>
#include <PubSubClient.h>
#include <DHT.h> // library for getting data from DHT
// Enter your WiFi ssid and password
const char* ssid = "TP-Link_DBCA"; //Provide your SSID
const char* password = "44388027"; // Provide Password
const char* mqtt_server = "a3k7086cinb3bt-ats.iot.us-west-2.amazonaws.com"; // Relace with your MQTT END point
const int mqtt_port = 8883;
String Read_rootca;
String Read_cert;
String Read_privatekey;
#define BUFFER_LEN 256
long lastMsg = 0;
char msg[BUFFER_LEN];
int Value = 0;
byte mac[6];
char mac_Id[18];
int count = 1;
WiFiClientSecure espClient;
PubSubClient client(espClient);
#define DHTPIN 4 //pin where the DHT22 is connected
DHT dht(DHTPIN, DHT11);
void setup_wifi() {
delay(10);
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
randomSeed(micros());
Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
}
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();
}
void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Create a random client ID
String clientId = "ESP32-";
clientId += String(random(0xffff), HEX);
// Attempt to connect
if (client.connect(clientId.c_str())) {
Serial.println("connected");
// Once connected, publish an announcement...
client.publish("ei_out", "hello world");
// ... and resubscribe
client.subscribe("ei_in");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}
void setup() {
Serial.begin(115200);
dht.begin();
// initialize digital pin LED_BUILTIN as an output.
pinMode(2, OUTPUT);
setup_wifi();
delay(1000);
//=============================================================
if (!SPIFFS.begin(true)) {
Serial.println("An Error has occurred while mounting SPIFFS");
return;
}
//=======================================
//Root CA File Reading.
File file2 = SPIFFS.open("/AmazonRootCA1.pem", "r");
if (!file2) {
Serial.println("Failed to open file for reading");
return;
}
Serial.println("Root CA File Content:");
while (file2.available()) {
Read_rootca = file2.readString();
Serial.println(Read_rootca);
}
//=============================================
// Cert file reading
File file4 = SPIFFS.open("/certificate.pem.crt.txt", "r");
if (!file4) {
Serial.println("Failed to open file for reading");
return;
}
Serial.println("Cert File Content:");
while (file4.available()) {
Read_cert = file4.readString();
Serial.println(Read_cert);
}
//=================================================
//Privatekey file reading
File file6 = SPIFFS.open("/private.pem.key", "r");
if (!file6) {
Serial.println("Failed to open file for reading");
return;
}
Serial.println("privateKey File Content:");
while (file6.available()) {
Read_privatekey = file6.readString();
Serial.println(Read_privatekey);
}
//=====================================================
char* pRead_rootca;
pRead_rootca = (char *)malloc(sizeof(char) * (Read_rootca.length() + 1));
strcpy(pRead_rootca, Read_rootca.c_str());
char* pRead_cert;
pRead_cert = (char *)malloc(sizeof(char) * (Read_cert.length() + 1));
strcpy(pRead_cert, Read_cert.c_str());
char* pRead_privatekey;
pRead_privatekey = (char *)malloc(sizeof(char) * (Read_privatekey.length() + 1));
strcpy(pRead_privatekey, Read_privatekey.c_str());
Serial.println("================================================================================================");
Serial.println("Certificates that passing to espClient Method");
Serial.println();
Serial.println("Root CA:");
Serial.write(pRead_rootca);
Serial.println("================================================================================================");
Serial.println();
Serial.println("Cert:");
Serial.write(pRead_cert);
Serial.println("================================================================================================");
Serial.println();
Serial.println("privateKey:");
Serial.write(pRead_privatekey);
Serial.println("================================================================================================");
espClient.setCACert(pRead_rootca);
espClient.setCertificate(pRead_cert);
espClient.setPrivateKey(pRead_privatekey);
client.setServer(mqtt_server, mqtt_port);
client.setCallback(callback);
//====================================================================================================================
WiFi.macAddress(mac);
snprintf(mac_Id, sizeof(mac_Id), "%02x:%02x:%02x:%02x:%02x:%02x",
mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
Serial.print(mac_Id);
//=====================================================================================================================
delay(2000);
}
void loop() {
float h = 80; // Reading Temperature form DHT sensor
float t = 22.5; // Reading Humidity form DHT sensor
float tF = (t * 1.8) + 32;
if (isnan(h) || isnan(t))
{
Serial.println("Failed to read from DHT sensor!");
return;
}
if (!client.connected()) {
reconnect();
}
client.loop();
long now = millis();
if (now - lastMsg > 2000) {
lastMsg = now;
//=============================================================================================
String macIdStr = mac_Id;
String Temprature = String(t);
String Humidity = String(h);
snprintf (msg, BUFFER_LEN, "{\"mac_Id\" : \"%s\", \"Temprature\" : %s, \"Humidity\" : \"%s\"}", macIdStr.c_str(), Temprature.c_str(), Humidity.c_str());
Serial.print("Publish message: ");
Serial.print(count);
Serial.println(msg);
client.publish("temp/", msg);
count = count + 1;
//================================================================================================
}
digitalWrite(2, HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000); // wait for a second
digitalWrite(2, LOW); // turn the LED off by making the voltage LOW
delay(1000); // wait for a second
}```