LTE TLS connection to MQTT Broker without CACert

SudoObey

I am using the Spresense main board with the LTE extension. I am using the Arduino IDE to flash the program to the device. I am trying to connect to a MQTT client using TLS but without having a CERT file. I just use a username and password. Is this something that is possible? Currently I am using LTETLSClient and MqttClient arduino libraries.

#include <LTE.h>
#include <ArduinoMqttClient.h>
#include <Arduino_JSON.h>

// APN name
#define APP_LTE_APN "apn.com"

// APN IP type
#define APP_LTE_IP_TYPE (LTE_NET_IPTYPE_V4V6)

// APN authentication type
#define APP_LTE_AUTH_TYPE (LTE_NET_AUTHTYPE_NONE) 

// RAT to use
#define APP_LTE_RAT (LTE_NET_RAT_CATM) 

LTE lteAccess;
LTETLSClient client;
MqttClient mqttClient(client);

// MQTT settings (WEST IOT)
const char broker[] = "mqtt.broker.com";
int port = 8883;
const char uname[] = "username";
const char client_id[] = "clientId";
const char pass[] = "password";

void setup()
{
  char apn[LTE_NET_APN_MAXLEN] = APP_LTE_APN;
  LTENetworkAuthType authtype = APP_LTE_AUTH_TYPE;

  // initialize serial communications and wait for port to open:
  Serial.begin(115200);
  while (!Serial) 
  {
      ; // wait for serial port to connect. Needed for native USB port only
  }
  while (true) 
  {
    /* Power on the modem and Enable the radio function. */
    if (lteAccess.begin() != LTE_SEARCHING) 
    {
      Serial.println("Could not transition to LTE_SEARCHING.");
      Serial.println("Please check the status of the LTE board.");
      for (;;) {
        sleep(1);
      }
    }

    /* The connection process to the APN will start.
     * If the synchronous parameter is false,
     * the return value will be returned when the connection process is started.
     */
    if (lteAccess.attach(APP_LTE_RAT,
                         apn,
                         "",
                         "",
                         authtype,
                         APP_LTE_IP_TYPE) == LTE_READY) 
    {
      Serial.println("attach succeeded.");
      break;
    }

    /* If the following logs occur frequently, one of the following might be a cause:
     * - APN settings are incorrect
     * - SIM is not inserted correctly
     * - If you have specified LTE_NET_RAT_NBIOT for APP_LTE_RAT,
     *   your LTE board may not support it.
     * - Rejected from LTE network
     */
    Serial.println("An error has occurred. Shutdown and retry the network attach process after 1 second.");
    lteAccess.shutdown();
    sleep(1);
  }

  Serial.print("Attempting to connect to the MQTT broker: ");
  Serial.println(broker);
  mqttClient.setUsernamePassword(uname, pass);
  mqttClient.setId(client_id);
  if (!mqttClient.connect(broker, port)) 
  {
    Serial.print("MQTT connection failed! Error code = ");
    Serial.println(mqttClient.connectError());
    while (1);
  }
  Serial.println("You're connected to the MQTT broker!");
  Serial.println();
}

CamilaSouza

Hey, SudoObey

I believe the TLS protocol requires a certificate.
Are you unsure of where to get the certificate you need?

SudoObey

@CamilaSouza
Thank you for getting back to me. I am fairly new to this MQTT and LTE thing. Is there a way to have a TLS connection using PSK without a Cert file?

Hi,
have you tried using the 'unsecure' MQTT port 1883?
Using this one you should not need a certificate or PSK.
BR