Unable to connect AWS IoT with umqtt.robust2 (CA-253)

[vivekmystrey]

MCU: ESP32-S3 Version: GENERIC_S3-20220618-v1.19.1

With umqtt.robust2 unable to publish messages to AWS IoT Cloud and there is no error too. While, with umqtt.robust it works properly for below script with ESP32-C3 for version v1.17 and message is received successfully in AWS.

Have used micropython version - v.1.19 and his error is common with both ESP32-C3 and ESP32-S3.

And, below is my code snippet:

#AWS MQTT client cert example for esp8266 or esp32 running MicroPython 1.9
from umqtt.robust2 import MQTTClient
import time
import network
import machine
from machine import Pin, ADC
from time import sleep
import usocket as socket
import ujson

#Certs for ESP8266
CERT_FILE = "/flash/ESP32-Core.cert.pem"
KEY_FILE = "/flash/ESP32-Core.private.key"

#if you change the ClientId make sure update AWS policy
MQTT_CLIENT_ID = "basicPubSub"
MQTT_PORT = 8883

MQTT_KEEPALIVE_INTERVAL = 45
THING_NAME = "ESP32-Core1"
SHADOW_UPDATE_TOPIC = "/sdk/test/Python"

RESPONSE_RECEIVED = False

#if you change the topic make sure update AWS policy
MQTT_TOPIC = "esp8266-topic"

#Change the following three settings to match your environment
MQTT_HOST = "*******************-ats.iot.us-east-1.amazonaws.com"
WIFI_SSID = "*************"
WIFI_PW = "************"

mqtt_client = None

def sub_cb(topic, msg, retained, duplicate):
    print((topic, msg, retained, duplicate))

def connect_mqtt():
    try:
        with open(KEY_FILE, "r") as f:
            key = f.read()

        print("MQTT received KEY")

        with open(CERT_FILE, "r") as f:
            cert = f.read()

        print("MQTT received CERTIFICATE")

        mqtt_client = MQTTClient(client_id=MQTT_CLIENT_ID, server=MQTT_HOST, port=MQTT_PORT, keepalive=5000, ssl=True, ssl_params={"cert":cert, "key":key, "server_side":False})
        mqtt_client.connect()
        mqtt_client.set_callback(sub_cb)
        print("MQTT is connected")
        a = {"message": "Hello from IoT console"}
        try:
            print("Check Connection Isue", mqtt_client.is_conn_issue())
            mqtt_client.publish(SHADOW_UPDATE_TOPIC, ujson.dumps(a))
            print("Publish Message")
        except Exception as e:
            print('Cannot Publish' + str(e))

    except Exception as e:
        print('Cannot connect to MQTT ' + str(e))
        raise

def connect_wifi(ssid, pw):
    wlan = network.WLAN(network.STA_IF)

    if(wlan.isconnected()):
        wlan.disconnect()
    nets = wlan.scan()

    if not wlan.isconnected():

        wlan.active(True)
        wlan.connect(WIFI_SSID, WIFI_PW)
        while not wlan.isconnected():
            pass
    print("Connected as:", wlan.ifconfig())

try:
    print("Connecting to WIFI...")
    connect_wifi(WIFI_SSID, WIFI_PW)
    print("Connecting to MQTT...")
    connect_mqtt()
    print("OK")

except Exception as e:
    print(str(e))

And, on enabling debug mode and get following response:

>>> %Run -c $EDITOR_CONTENT
Connecting to WIFI...
Connected as: ('192.***.*.*', '255.255.255.0', '192.***.*.*', '192.***.*.*')
Connecting to MQTT...
MQTT received KEY
MQTT received CERTIFICATE
MQTT is connected
MQTT (connect): MQTTException(1,)
Publish Message
OK

Can you please, help why the connection get closed after it is connected? Below is the snippet of ESP32-S3 filesystem: