Perform HTTP request on backend to retrieve secure endpoint location
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154
esp32_device/main/http_client.c
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154
esp32_device/main/http_client.c
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#include "http_client.h"
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#include "esp_http_client.h"
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#include "esp_tls.h"
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#include "esp_log.h"
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#include <sys/param.h>
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#include <string.h>
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#define MAX_HTTP_RECV_BUFFER 512
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#define MAX_HTTP_OUTPUT_BUFFER 2048
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static const char *TAG = "http_client";
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esp_err_t _http_event_handler(esp_http_client_event_t *evt)
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{
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static char *output_buffer; // Buffer to store response of http request from event handler
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static int output_len; // Stores number of bytes read
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switch (evt->event_id)
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{
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case HTTP_EVENT_ERROR:
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ESP_LOGD(TAG, "HTTP_EVENT_ERROR");
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break;
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case HTTP_EVENT_ON_CONNECTED:
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ESP_LOGD(TAG, "HTTP_EVENT_ON_CONNECTED");
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break;
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case HTTP_EVENT_HEADER_SENT:
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ESP_LOGD(TAG, "HTTP_EVENT_HEADER_SENT");
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break;
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case HTTP_EVENT_ON_HEADER:
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ESP_LOGD(TAG, "HTTP_EVENT_ON_HEADER, key=%s, value=%s", evt->header_key, evt->header_value);
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break;
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case HTTP_EVENT_ON_DATA:
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ESP_LOGD(TAG, "HTTP_EVENT_ON_DATA, len=%d", evt->data_len);
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// Clean the buffer in case of a new request
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if (output_len == 0 && evt->user_data)
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{
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// we are just starting to copy the output data into the use
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memset(evt->user_data, 0, MAX_HTTP_OUTPUT_BUFFER);
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}
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/*
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* Check for chunked encoding is added as the URL for chunked encoding used in this example returns binary data.
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* However, event handler can also be used in case chunked encoding is used.
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*/
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if (!esp_http_client_is_chunked_response(evt->client))
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{
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// If user_data buffer is configured, copy the response into the buffer
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int copy_len = 0;
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if (evt->user_data)
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{
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// The last byte in evt->user_data is kept for the NULL character in case of out-of-bound access.
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copy_len = MIN(evt->data_len, (MAX_HTTP_OUTPUT_BUFFER - output_len));
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if (copy_len)
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{
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memcpy(evt->user_data + output_len, evt->data, copy_len);
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}
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}
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else
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{
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int content_len = esp_http_client_get_content_length(evt->client);
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if (output_buffer == NULL)
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{
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// We initialize output_buffer with 0 because it is used by strlen() and similar functions therefore should be null terminated.
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output_buffer = (char *)calloc(content_len + 1, sizeof(char));
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output_len = 0;
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if (output_buffer == NULL)
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{
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ESP_LOGE(TAG, "Failed to allocate memory for output buffer");
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return ESP_FAIL;
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}
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}
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copy_len = MIN(evt->data_len, (content_len - output_len));
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if (copy_len)
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{
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memcpy(output_buffer + output_len, evt->data, copy_len);
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}
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}
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output_len += copy_len;
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}
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break;
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case HTTP_EVENT_ON_FINISH:
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ESP_LOGD(TAG, "HTTP_EVENT_ON_FINISH");
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if (output_buffer != NULL)
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{
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// Print buffer
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ESP_LOG_BUFFER_HEX(TAG, output_buffer, output_len);
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free(output_buffer);
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output_buffer = NULL;
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}
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output_len = 0;
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break;
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case HTTP_EVENT_DISCONNECTED:
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ESP_LOGI(TAG, "HTTP_EVENT_DISCONNECTED");
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int mbedtls_err = 0;
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esp_err_t err = esp_tls_get_and_clear_last_error((esp_tls_error_handle_t)evt->data, &mbedtls_err, NULL);
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if (err != 0)
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{
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ESP_LOGI(TAG, "Last esp error code: 0x%x", err);
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ESP_LOGI(TAG, "Last mbedtls failure: 0x%x", mbedtls_err);
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}
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if (output_buffer != NULL)
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{
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free(output_buffer);
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output_buffer = NULL;
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}
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output_len = 0;
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break;
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case HTTP_EVENT_REDIRECT:
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ESP_LOGD(TAG, "HTTP_EVENT_REDIRECT");
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esp_http_client_set_header(evt->client, "From", "user@example.com");
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esp_http_client_set_header(evt->client, "Accept", "text/html");
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esp_http_client_set_redirection(evt->client);
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break;
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}
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return ESP_OK;
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}
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char *http_client_exec(const http_request_opts *opts)
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{
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char local_response_buffer[MAX_HTTP_OUTPUT_BUFFER + 1] = {0};
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ESP_LOGI(TAG, "Perform HTTP request on %s", opts->url);
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esp_http_client_config_t config = {
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.event_handler = _http_event_handler,
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.user_data = local_response_buffer,
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.url = opts->url,
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.disable_auto_redirect = true,
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};
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esp_http_client_handle_t client = esp_http_client_init(&config);
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esp_err_t err = esp_http_client_perform(client);
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const int status = esp_http_client_get_status_code(client);
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const int64_t resp_len = esp_http_client_get_content_length(client);
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esp_http_client_cleanup(client);
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if (err != ESP_OK)
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{
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ESP_LOGE(TAG, "HTTP request failed with code %xd!", err);
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return NULL;
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}
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if (status < 200 || status > 299)
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{
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ESP_LOGE(TAG, "HTTP request failed with status %d!", status);
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return NULL;
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}
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local_response_buffer[resp_len] = 0;
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return strdup(local_response_buffer);
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}
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