Thanks for producing the book. In a short time I got FTP camera images to work thanks to the book.

e#include "sdkconfig.h" // used for log printing
#include "esp_system.h"
#include "freertos/FreeRTOS.h" //freeRTOS items to be used
#include "freertos/task.h"
#include "certs.h"
#include "esp_camera.h"
#include "soc/soc.h"           
#include "soc/rtc_cntl_reg.h"  
#include "driver/rtc_io.h"
#include <WiFi.h>
#include <WiFiClient.h>
#include "ESP32_FTPClient.h"
//
WiFiClient   wifiClient; // do the WiFi instantiation thing
ESP32_FTPClient ftp (ftp_server, ftp_user, ftp_pass, 5000, 2);
//
// Pin definition for CAMERA_MODEL_AI_THINKER
// Change pin definition if you're using another ESP32 with camera module
#define PWDN_GPIO_NUM     32
#define RESET_GPIO_NUM    -1
#define XCLK_GPIO_NUM      0
#define SIOD_GPIO_NUM     26
#define SIOC_GPIO_NUM     27
#define Y9_GPIO_NUM       35
#define Y8_GPIO_NUM       34
#define Y7_GPIO_NUM       39
#define Y6_GPIO_NUM       36
#define Y5_GPIO_NUM       21
#define Y4_GPIO_NUM       19
#define Y3_GPIO_NUM       18
#define Y2_GPIO_NUM        5
#define VSYNC_GPIO_NUM    25
#define HREF_GPIO_NUM     23
#define PCLK_GPIO_NUM     22
////
void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
{
  switch (event) {
    case SYSTEM_EVENT_STA_CONNECTED:
      log_i("Connected to WiFi access point");
      break;
    case SYSTEM_EVENT_STA_DISCONNECTED:
      log_i("Disconnected from WiFi access point");
      break;
    case SYSTEM_EVENT_AP_STADISCONNECTED:
      log_i("WiFi client disconnected");
      break;
    default: break;
  }
} // void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
////
void setup()
{
  WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 0); //disable brownout detector
  ////
  configInitCamera();
  //
  xTaskCreatePinnedToCore( capturePhoto_sendFTP, "capturePhoto_sendFTP", 20000, NULL, 3, NULL, 1 );
} // void setup()
////
void capturePhoto_sendFTP( void *pvParameters )
{
  TickType_t xLastWakeTime    = xTaskGetTickCount();
  const TickType_t xFrequency = 1000 * 15; //delay for mS
  for (;;)
  {
    log_i( "tick");
    if ( WiFi.status() == WL_CONNECTED )
    {
      camera_fb_t * fb = NULL; // pointer
      fb = esp_camera_fb_get();
      if (!fb)
      {
        log_i( "Camera capture failed" );
      } else {
        ftp.OpenConnection(); // try open FTP
        if ( ftp.isConnected() )
        {
          //try send file ftp to RPi
          ftp.ChangeWorkDir( ftp_path ); 
          // Delete existing file, create the new file, and send the image to the file
          ftp.DeleteFile( ftp_file_name );
          ftp.InitFile( ftp_file_type );
          ftp.NewFile( ftp_file_name );
          log_i( "length %d", fb->len );
          //void WriteData (unsigned char * data, int dataLength); //Convert image to unsigned character data format for sending FTP
          ftp.WriteData( (unsigned char *)fb->buf, fb->len ); 
          ftp.CloseFile();
          ftp.CloseConnection();
        }
        esp_camera_fb_return(fb); //return the frame buffer back to the driver for reuse
      }
    } else {
      log_i( "In capturePhoto_sendFTP found WiFi not connected ");
      connectToWiFi();
    }
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
  }
  vTaskDelete( NULL );
} //void capturePhoto_sendFTP( void *pvParameters )
////
void configInitCamera()
{
  // Stores the camera configuration parameters
  camera_config_t config;
  config.ledc_channel = LEDC_CHANNEL_0;
  config.ledc_timer = LEDC_TIMER_0;
  config.pin_d0 = Y2_GPIO_NUM;
  config.pin_d1 = Y3_GPIO_NUM;
  config.pin_d2 = Y4_GPIO_NUM;
  config.pin_d3 = Y5_GPIO_NUM;
  config.pin_d4 = Y6_GPIO_NUM;
  config.pin_d5 = Y7_GPIO_NUM;
  config.pin_d6 = Y8_GPIO_NUM;
  config.pin_d7 = Y9_GPIO_NUM;
  config.pin_xclk = XCLK_GPIO_NUM;
  config.pin_pclk = PCLK_GPIO_NUM;
  config.pin_vsync = VSYNC_GPIO_NUM;
  config.pin_href = HREF_GPIO_NUM;
  config.pin_sscb_sda = SIOD_GPIO_NUM;
  config.pin_sscb_scl = SIOC_GPIO_NUM;
  config.pin_pwdn = PWDN_GPIO_NUM;
  config.pin_reset = RESET_GPIO_NUM;
  config.xclk_freq_hz = 20000000;
  config.pixel_format = PIXFORMAT_JPEG;
  // Select lower framesize if the camera doesn't support PSRAM
  if (psramFound()) {
    config.frame_size = FRAMESIZE_UXGA; // FRAMESIZE_ + QVGA|CIF|VGA|SVGA|XGA|SXGA|UXGA
    config.jpeg_quality = 10; //0-63 lower number means higher quality
    config.fb_count = 2;
  } else {
    config.frame_size = FRAMESIZE_SVGA;
    config.jpeg_quality = 12;
    config.fb_count = 1;
  }
  // Initialize the Camera
  esp_err_t err = esp_camera_init(&config);
  if (err != ESP_OK) {
    log_i("Camera init failed with error 0x%x", err);
    return;
  }
} //void configInitCamera()
////
void connectToWiFi()
{
  int TryCount = 0;
  while ( WiFi.status() != WL_CONNECTED )
  {
    TryCount++;
    WiFi.disconnect();
    WiFi.begin( SSID, PASSWORD );
    vTaskDelay( 4000 );
    if ( TryCount == 10 )
    {
      ESP.restart();
    }
  }
  WiFi.onEvent( WiFiEvent );
}
////
void loop() {}

I share my code and hope another may find it useful. Again Thanks for producing the book.