simple "HTTP by hand" in ESP-IDF

http_request_byhand.c

// simple "HTTP by hand" in ESP-IDF
// add "REQUIRES esp_wifi esp_netif nvs_flash" to CMakeLists.txt

#include <string.h>
#include <sys/socket.h>
#include <netdb.h>      // getaddrinfo()
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "nvs_flash.h"


const char* my_wifi_ssid = "myssidismypassport";
const char* my_wifi_pass = "setectastronomy";

const char* url_hostname = "todbot.com";
const char* url_path = "/tst/randcolor.php";

static const char *TAG = "HTTP_TOD";

// note this does not wait for wifi to connect
static void wifi_init(const char *wifi_ssid, const char *wifi_pass) {
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());
    esp_netif_create_default_wifi_sta();

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK(esp_wifi_init(&cfg));

    /* if using #defines, can do this */
    /* wifi_config_t wifi_config = { */
    /*     .sta = { */
    /*         .ssid = WIFI_SSID, */
    /*         .password = WIFI_PASS, */
    /*     }, */
    /* }; */
    /* but for in-memory strings, need to strncpy() the exact length */
    
    wifi_config_t wifi_config = {0}; // empty config
    strncpy((char *)wifi_config.sta.ssid, wifi_ssid, sizeof(wifi_config.sta.ssid));
    strncpy((char *)wifi_config.sta.password, wifi_pass, sizeof(wifi_config.sta.password));
    
    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
    ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config));
    ESP_ERROR_CHECK(esp_wifi_start());
    ESP_ERROR_CHECK(esp_wifi_connect());
}

static void http_get(const char *host, const char *path) {
    struct addrinfo hints = {
        .ai_family = AF_INET,
        .ai_socktype = SOCK_STREAM,
    };
    struct addrinfo *res;
    int s;

    char port_str[] = "80";
    int err = getaddrinfo(host, port_str, &hints, &res);
    if (err != 0 || res == NULL) {
        ESP_LOGE(TAG, "DNS lookup failed for %s", host);
        return;
    }

    s = socket(res->ai_family, res->ai_socktype, 0);
    if (s < 0) {
        ESP_LOGE(TAG, "socket failed");
        freeaddrinfo(res);
        return;
    }

    if (connect(s, res->ai_addr, res->ai_addrlen) != 0) {
        ESP_LOGE(TAG, "connect failed");
        close(s);
        freeaddrinfo(res);
        return;
    }

    freeaddrinfo(res);

    char req[128];
    snprintf(req, sizeof(req),
             "GET %s HTTP/1.0\r\n"
             "Host: %s\r\n"
             "User-Agent: esp-idf/5.5\r\n"
             "\r\n",
             path, host);

    if (write(s, req, strlen(req)) < 0) {
        ESP_LOGE(TAG, "send failed");
        close(s);
        return;
    }

    char recv_buf[512];
    int r;
    while ((r = read(s, recv_buf, sizeof(recv_buf) - 1)) > 0) {
        recv_buf[r] = 0; // null terminate
        printf("%s", recv_buf);
    }
    close(s);
}

void app_main(void) {
    printf("-------- app startup \n"); // this eliminates the USB disconnect/reconnect? 
    ESP_LOGI(TAG, "-------- App startup \n");
    ESP_ERROR_CHECK(nvs_flash_init());

    ESP_LOGI(TAG, "-------- Waiting 5 seconds for USB to start\n");
    vTaskDelay(pdMS_TO_TICKS(5000)); // wait for USB to connect
    
    ESP_LOGI(TAG, "-------- Connecting to WiFi and waiting 5 seconds...\n");
    
    wifi_init(my_wifi_ssid, my_wifi_pass);
    
    ESP_LOGI(TAG, "-------- Connected.\n");

    vTaskDelay(pdMS_TO_TICKS(5000)); // wait for WiFi to connect

    while(1) { 
        http_get(url_hostname, url_path);
        printf("\n");
        vTaskDelay(pdMS_TO_TICKS(10*1000)); // wait before doing it all again
    }
        
}