ESP32 test code for wifi scan + mqtt

scan_mqtt.c

/* Scan Example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/

/*
   this example shows how to use all channel scan or fast scan to connect
   In the fast scan mode, scan will end after find matched AP, in this mode, you
   can set the threshold of auth mode and signal, the filter will ignore the AP
   whose auth mode and rssi below the threshold.
   In the all channel scan, scan will end after scan all the channel, and will
   the best AP to connect, you can sort by signal or auth mode, auth mode is follow
   the rule WPA2>WPA>WEP.
*/
#include <string.h>

#include "freertos/FreeRTOS.h"
#include "freertos/event_groups.h"
#include "esp_wifi.h"
#include "esp_log.h"
#include "esp_event_loop.h"
#include "nvs_flash.h"
#include "esp_mqtt.h"

/*set the ssid and password via "make menuconfig"*/
#define DEFAULT_SSID CONFIG_WIFI_SSID
#define DEFAULT_PWD CONFIG_WIFI_PASSWORD

#if CONFIG_WIFI_ALL_CHANNEL_SCAN
#define DEFAULT_SCAN_METHOD WIFI_ALL_CHANNEL_SCAN
#elif CONFIG_WIFI_FAST_SCAN
#define DEFAULT_SCAN_METHOD WIFI_FAST_SCAN
#else
#define DEFAULT_SCAN_METHOD WIFI_FAST_SCAN
#endif /*CONFIG_SCAN_METHOD*/

#if CONFIG_WIFI_CONNECT_AP_BY_SIGNAL
#define DEFAULT_SORT_METHOD WIFI_CONNECT_AP_BY_SIGNAL
#elif CONFIG_WIFI_CONNECT_AP_BY_SECURITY
#define DEFAULT_SORT_METHOD WIFI_CONNECT_AP_BY_SECURITY
#else
#define DEFAULT_SORT_METHOD WIFI_CONNECT_AP_BY_SIGNAL
#endif /*CONFIG_SORT_METHOD*/

#if CONFIG_FAST_SCAN_THRESHOLD
#define DEFAULT_RSSI CONFIG_FAST_SCAN_MINIMUM_SIGNAL
#if CONFIG_EXAMPLE_OPEN
#define DEFAULT_AUTHMODE WIFI_AUTH_OPEN
#elif CONFIG_EXAMPLE_WEP
#define DEFAULT_AUTHMODE WIFI_AUTH_WEP
#elif CONFIG_EXAMPLE_WPA
#define DEFAULT_AUTHMODE WIFI_AUTH_WPA_PSK
#elif CONFIG_EXAMPLE_WPA2
#define DEFAULT_AUTHMODE WIFI_AUTH_WPA2_PSK
#else
#define DEFAULT_AUTHMODE WIFI_AUTH_OPEN
#endif
#else
#define DEFAULT_RSSI -127
#define DEFAULT_AUTHMODE WIFI_AUTH_OPEN
#endif /*CONFIG_FAST_SCAN_THRESHOLD*/

static const char *TAG = "scan";

static esp_err_t event_handler(void *ctx, system_event_t *event)
{
    switch(event->event_id) {
    case SYSTEM_EVENT_STA_START:
	ESP_LOGI(TAG, "SYSTEM_EVENT_STA_START");
	ESP_ERROR_CHECK(esp_wifi_connect());
	break;
    case SYSTEM_EVENT_STA_GOT_IP:
	ESP_LOGI(TAG, "SYSTEM_EVENT_STA_GOT_IP");
	ESP_LOGI(TAG, "got ip:%s\n",
		ip4addr_ntoa(&event->event_info.got_ip.ip_info.ip));

    esp_mqtt_init(NULL, NULL, 256, 2000);
    esp_mqtt_start("test.mosquitto.org", 1883, "MAS_ESP", NULL, NULL);
    static const char *payload = "Hello from ESP!";
    esp_mqtt_publish("test/mymytopic", (void *)payload, (int)strlen(payload), 0, 0);


        break;
    case SYSTEM_EVENT_STA_DISCONNECTED:
	ESP_LOGI(TAG, "SYSTEM_EVENT_STA_DISCONNECTED");
	ESP_ERROR_CHECK(esp_wifi_connect());
	break;
    default:
        break;
    }
    return ESP_OK;
}

/*init wifi as sta and set scan method*/
static void wifi_scan(void)
{
    tcpip_adapter_init();
    ESP_ERROR_CHECK(esp_event_loop_init(event_handler, NULL));

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK(esp_wifi_init(&cfg));
    wifi_config_t wifi_config = {
	.sta = {
	    .ssid = DEFAULT_SSID,
	    .password = DEFAULT_PWD,
            .scan_method = DEFAULT_SCAN_METHOD,
            .sort_method = DEFAULT_SORT_METHOD,
            .threshold.rssi = DEFAULT_RSSI,
            .threshold.authmode = DEFAULT_AUTHMODE,
	},
    };
    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
    ESP_ERROR_CHECK(esp_wifi_set_config(ESP_IF_WIFI_STA, &wifi_config));
    ESP_ERROR_CHECK(esp_wifi_start());
}

void app_main()
{
    // Initialize NVS
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES) {
        ESP_ERROR_CHECK(nvs_flash_erase());
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK( ret );

    wifi_scan();
}