MQTT ssl connection error

[maldus]

Hello,
I'm trying to connect an ESP32S2 module to an MQTT broker. The connection requires SSL authentication and I have a couple of certificates to use. I copied the MQTT SSL example (https://github.com/espressif/esp-idf/bl ... app_main.c), removed all the subscription/unsubscription/send operations and added my own certificates just to test if the connection worked.

At the moment the connection fails; while I admit my experience with MQTT is limited the error printed out looks a bit obscure to me:

Code: Select all

I (777) WiFi: Wifi Successfully connected
I (857) wifi:AP's beacon interval = 102400 us, DTIM period = 1
I (3967) WiFi: got ip:192.168.1.159
I (3967) Http Server: Started
I (3967) esp_netif_handlers: sta ip: 192.168.1.159, mask: 255.255.255.0, gw: 192.168.1.1
I (3967) MQTTS_EXAMPLE: Other event id:7
W (3977) wifi:<ba-add>idx:0 (ifx:0, 04:f0:21:4f:17:88), tid:0, ssn:0, winSize:64
E (6617) MQTT_CLIENT: mqtt_message_receive: transport_read() error: errno=0
I (6617) MQTTS_EXAMPLE: MQTT_EVENT_ERROR
I (6617) MQTTS_EXAMPLE: Last error code reported from esp-tls: 0x0
I (6617) MQTTS_EXAMPLE: Last tls stack error number: 0x0
I (6627) MQTTS_EXAMPLE: Last captured errno : 0 (Success)
E (6637) MQTT_CLIENT: esp_mqtt_connect: mqtt_message_receive() returned -1
E (6637) MQTT_CLIENT: MQTT connect failed

While it's specified that `mqtt_message_receive` returns -1 the errno code is 0 (which should mean everything is fine?). I can't understand if I somehow messed up the certificates or something else.

For reference, here is the complete module. `cloud_init` is called at startup, while `cloud_mqtt_connection_start` is invoked once a suitable network connection is established:

Code: Select all

#include <stdio.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include "esp_system.h"
#include "nvs_flash.h"
#include "esp_event.h"
#include "esp_netif.h"
#include "freertos/FreeRTOS.h"
#include "freertos/semphr.h"
#include "esp_log.h"
#include "mqtt_client.h"
#include "esp_tls.h"
#include "esp_ota_ops.h"
#include <sys/param.h>
#include "config/app_config.h"


static const char *TAG = "MQTTS_EXAMPLE";

extern const uint8_t mqtt_ca_pem_start[] asm("_binary_mqtt_ca_pem_start");
extern const uint8_t mqtt_ca_pem_end[] asm("_binary_mqtt_ca_pem_end");

extern const uint8_t mqtt_certificate_pem_start[] asm("_binary_mqtt_certificate_pem_start");
extern const uint8_t mqtt_certificate_pem_end[] asm("_binary_mqtt_certificate_pem_end");

extern const uint8_t mqtt_private_pem_start[] asm("_binary_mqtt_private_pem_start");
extern const uint8_t mqtt_private_pem_end[] asm("_binary_mqtt_private_pem_end");

static SemaphoreHandle_t        sem    = NULL;
static esp_mqtt_client_handle_t client = NULL;


static void send_binary(esp_mqtt_client_handle_t client) {
    spi_flash_mmap_handle_t out_handle;
    const void *            binary_address;
    const esp_partition_t * partition = esp_ota_get_running_partition();
    esp_partition_mmap(partition, 0, partition->size, SPI_FLASH_MMAP_DATA, &binary_address, &out_handle);
    // sending only the configured portion of the partition (if it's less than the partition size)
    int binary_size = MIN(1024, partition->size);
    int msg_id      = esp_mqtt_client_publish(client, "/topic/binary", binary_address, binary_size, 0, 0);
    ESP_LOGI(TAG, "binary sent with msg_id=%d", msg_id);
}


static esp_err_t mqtt_event_handler_cb(esp_mqtt_event_handle_t event) {
    esp_mqtt_client_handle_t client = event->client;
    int                      msg_id;
    // your_context_t *context = event->context;
    switch (event->event_id) {
        case MQTT_EVENT_CONNECTED:
            ESP_LOGI(TAG, "MQTT_EVENT_CONNECTED");
            // msg_id = esp_mqtt_client_subscribe(client, "/topic/qos0", 0);
            // ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id);
            break;
        case MQTT_EVENT_DISCONNECTED:
            ESP_LOGI(TAG, "MQTT_EVENT_DISCONNECTED");
            break;

        case MQTT_EVENT_SUBSCRIBED:
            ESP_LOGI(TAG, "MQTT_EVENT_SUBSCRIBED, msg_id=%d", event->msg_id);
            // msg_id = esp_mqtt_client_publish(client, "/topic/qos0", "data", 0, 0, 0);
            // ESP_LOGI(TAG, "sent publish successful, msg_id=%d", msg_id);
            break;
        case MQTT_EVENT_UNSUBSCRIBED:
            ESP_LOGI(TAG, "MQTT_EVENT_UNSUBSCRIBED, msg_id=%d", event->msg_id);
            break;
        case MQTT_EVENT_PUBLISHED:
            ESP_LOGI(TAG, "MQTT_EVENT_PUBLISHED, msg_id=%d", event->msg_id);
            break;
        case MQTT_EVENT_DATA:
            ESP_LOGI(TAG, "MQTT_EVENT_DATA");
            printf("TOPIC=%.*s\r\n", event->topic_len, event->topic);
            printf("DATA=%.*s\r\n", event->data_len, event->data);
            /*if (strncmp(event->data, "send binary please", event->data_len) == 0) {
                ESP_LOGI(TAG, "Sending the binary");
                send_binary(client);
            }*/
            break;
        case MQTT_EVENT_ERROR:
            ESP_LOGI(TAG, "MQTT_EVENT_ERROR");
            if (event->error_handle->error_type == MQTT_ERROR_TYPE_TCP_TRANSPORT) {
                ESP_LOGI(TAG, "Last error code reported from esp-tls: 0x%x", event->error_handle->esp_tls_last_esp_err);
                ESP_LOGI(TAG, "Last tls stack error number: 0x%x", event->error_handle->esp_tls_stack_err);
                ESP_LOGI(TAG, "Last captured errno : %d (%s)", event->error_handle->esp_transport_sock_errno,
                         strerror(event->error_handle->esp_transport_sock_errno));
            } else if (event->error_handle->error_type == MQTT_ERROR_TYPE_CONNECTION_REFUSED) {
                ESP_LOGI(TAG, "Connection refused error: 0x%x", event->error_handle->connect_return_code);
            } else {
                ESP_LOGW(TAG, "Unknown error type: 0x%x", event->error_handle->error_type);
            }
            break;
        default:
            ESP_LOGI(TAG, "Other event id:%d", event->event_id);
            break;
    }
    return ESP_OK;
}


static void mqtt_event_handler(void *handler_args, esp_event_base_t base, int32_t event_id, void *event_data) {
    ESP_LOGD(TAG, "Event dispatched from event loop base=%s, event_id=%d", base, event_id);
    mqtt_event_handler_cb(event_data);
}


void cloud_mqtt_connection_stop(void) {
    xSemaphoreTake(sem, portMAX_DELAY);
    if (client != NULL) {
        esp_mqtt_client_stop(client);
    }
    xSemaphoreGive(sem);
}


void cloud_mqtt_connection_start(void) {
    xSemaphoreTake(sem, portMAX_DELAY);
    if (client == NULL) {
        const esp_mqtt_client_config_t mqtt_cfg = {
            .uri             = MQTT_BROKER_URI,
            .port            = 8883,
            .cert_pem        = (const char *)mqtt_ca_pem_start,
            .cert_len        = (mqtt_ca_pem_end - mqtt_ca_pem_start),
            .client_cert_pem = (const char *)mqtt_certificate_pem_start,
            .client_cert_len = (mqtt_certificate_pem_end - mqtt_certificate_pem_start),
            .client_key_pem  = (const char *)mqtt_private_pem_start,
            .client_key_len  = (mqtt_private_pem_end - mqtt_private_pem_start),
        };

        client = esp_mqtt_client_init(&mqtt_cfg);
        esp_mqtt_client_register_event(client, ESP_EVENT_ANY_ID, mqtt_event_handler, client);
    }
    esp_mqtt_client_start(client);
    xSemaphoreGive(sem);
}


void cloud_init(void) {
    static StaticSemaphore_t buffer;
    sem = xSemaphoreCreateMutexStatic(&buffer);

    esp_log_level_set("*", ESP_LOG_INFO);
    esp_log_level_set("esp-tls", ESP_LOG_VERBOSE);
    esp_log_level_set("MQTT_CLIENT", ESP_LOG_VERBOSE);
    esp_log_level_set("MQTT_EXAMPLE", ESP_LOG_VERBOSE);
    esp_log_level_set("TRANSPORT_TCP", ESP_LOG_VERBOSE);
    esp_log_level_set("TRANSPORT_SSL", ESP_LOG_VERBOSE);
    esp_log_level_set("TRANSPORT", ESP_LOG_VERBOSE);
    esp_log_level_set("OUTBOX", ESP_LOG_VERBOSE);
}

[maldus]

I found the issue: I was forgetting to set a specific `client_id`. Still, the error message could probably be improved.

[jhonydotnet]

Hello, I leave this in case it helps someone. I had the same error and I fixed it by making the client_id of the MQTT configuration not the same between ESP32 connected to the broker.
Greetings