MQTT_Client Problem

[arnold.braun@gmx.de]

Hello,

i played around with the mqtt demo and extend it just for webserver. Everything worked. Suddenly i cant compile again and get the following error

Target 'component-xtensa-debug-module-build' responsible for 'C:/Workbench/ESP32/esp32-webserver/build/xtensa-debug-module/libxtensa-debug-module.a'
C:/Workbench/ESP32/esp32-webserver/build/main\libmain.a(main.o):(.literal._ZL18mqtt_event_handlerP16esp_mqtt_event_t+0x44): undefined reference to `esp_mqtt_client_subscribe(esp_mqtt_client*, char const*, int)'
C:/Workbench/ESP32/esp32-webserver/build/main\libmain.a(main.o):(.literal._ZL18mqtt_event_handlerP16esp_mqtt_event_t+0x48): undefined reference to `esp_mqtt_client_unsubscribe(esp_mqtt_client*, char const*)'
C:/Workbench/ESP32/esp32-webserver/build/main\libmain.a(main.o):(.literal._ZL18mqtt_event_handlerP16esp_mqtt_event_t+0x4c): undefined reference to `esp_mqtt_client_publish(esp_mqtt_client*, char const*, char const*, int, int, int)'
C:/Workbench/ESP32/esp32-webserver/build/main\libmain.a(main.o):(.literal.mqtt_app_start+0x14): undefined reference to `esp_mqtt_client_init(esp_mqtt_client_config_t const*)'
C:/Workbench/ESP32/esp32-webserver/build/main\libmain.a(main.o):(.literal.mqtt_app_start+0x18): undefined reference to `esp_mqtt_client_start(esp_mqtt_client*)'
C:/Workbench/ESP32/esp32-webserver/build/main\libmain.a(main.o): In function `mqtt_event_handler(esp_mqtt_event_t*)':
C:/Workbench/ESP32/esp32-webserver/main/main.cpp:491: undefined reference to `esp_mqtt_client_subscribe(esp_mqtt_client*, char const*, int)'
C:/Workbench/ESP32/esp32-webserver/main/main.cpp:491: undefined reference to `esp_mqtt_client_subscribe(esp_mqtt_client*, char const*, int)'
C:/Workbench/ESP32/esp32-webserver/main/main.cpp:491: undefined reference to `esp_mqtt_client_unsubscribe(esp_mqtt_client*, char const*)'
C:/Workbench/ESP32/esp32-webserver/main/main.cpp:491: undefined reference to `esp_mqtt_client_publish(esp_mqtt_client*, char const*, char const*, int, int, int)'
C:/Workbench/ESP32/esp32-webserver/build/main\libmain.a(main.o): In function `mqtt_app_start':
C:/Workbench/ESP32/esp32-webserver/main/main.cpp:507: undefined reference to `esp_mqtt_client_init(esp_mqtt_client_config_t const*)'
C:/Workbench/ESP32/esp32-webserver/main/main.cpp:508: undefined reference to `esp_mqtt_client_start(esp_mqtt_client*)'
C:/Workbench/ESP32/esp32-webserver/main/main.cpp:511: undefined reference to `esp_mqtt_client_publish(esp_mqtt_client*, char const*, char const*, int, int, int)'

SRC

#include "mqtt_client.h"
extern "C" void mqtt_app_start(void)
{
esp_mqtt_client_config_t mqtt_cfg = {};


strncpy(mqtt_cfg.uri, "mqtt://192.168.178.22", sizeof(mqtt_cfg.uri));
mqtt_cfg.event_handle = mqtt_event_handler;

esp_mqtt_client_handle_t client = esp_mqtt_client_init(&mqtt_cfg);
esp_mqtt_client_start(client);
mqttclient = client;

int msg_id = esp_mqtt_client_publish(mqttclient, "/topic/qos0", "test Loop first", 0, 0, 0);
}

static esp_err_t mqtt_event_handler(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);

msg_id = esp_mqtt_client_subscribe(client, "/topic/qos1", 1);
ESP_LOGI(TAG, "sent subscribe successful, msg_id=%d", msg_id);

msg_id = esp_mqtt_client_unsubscribe(client, "/topic/qos1");
ESP_LOGI(TAG, "sent unsubscribe 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);
break;
case MQTT_EVENT_ERROR:
ESP_LOGI(TAG, "MQTT_EVENT_ERROR");
break;
}


return ESP_OK;
}


And the line numbers in the Error Messages don´t match to the real line nr.


Of course the library is included.
i don´t know why

[arnold.braun@gmx.de]

after i put this in, it works.

extern "C" {
#include "mqtt_client.h"
}

i just don´t understand why before it worked without this. For me its like try and error.

[kolban]

Howdy,
In your first post you said you were working with "the" MQTT demo. Where would that be found? I think there might be a few MQTT ESP32 libraries and I'm curious which one you were looking at.