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/* BSD Socket API 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.

*/

#include <string.h>

#include <sys/param.h>

#include "freertos/FreeRTOS.h"

#include "freertos/task.h"

#include "freertos/event_groups.h"

#include "esp_system.h"

#include "esp_wifi.h"

#include "esp_event_loop.h"

#include "esp_log.h"

#include "nvs_flash.h"



#include "lwip/err.h"

#include "lwip/sockets.h"

#include "lwip/sys.h"

#include <lwip/netdb.h>





/* The examples use simple WiFi configuration that you can set via

   'make menuconfig'.

   If you'd rather not, just change the below entries to strings with

   the config you want - ie #define EXAMPLE_WIFI_SSID "mywifissid"

*/

#define EXAMPLE_WIFI_SSID CONFIG_WIFI_SSID

#define EXAMPLE_WIFI_PASS CONFIG_WIFI_PASSWORD



#define PORT CONFIG_EXAMPLE_PORT



/* FreeRTOS event group to signal when we are connected & ready to make a request */

static EventGroupHandle_t wifi_event_group;



const int IPV4_GOTIP_BIT = BIT0;



static const char *TAG = "example";



static esp_err_t event_handler(void *ctx, system_event_t *event)

{

    switch (event->event_id) {

    case SYSTEM_EVENT_STA_START:

        esp_wifi_connect();

        ESP_LOGI(TAG, "SYSTEM_EVENT_STA_START");

        break;

    case SYSTEM_EVENT_STA_CONNECTED:

    	ESP_LOGI(TAG, "SYSTEM_EVENT_STA_CONNECTED");

    	break;

    case SYSTEM_EVENT_STA_GOT_IP:

        xEventGroupSetBits(wifi_event_group, IPV4_GOTIP_BIT);

        ESP_LOGI(TAG, "SYSTEM_EVENT_STA_GOT_IP");

        break;

    case SYSTEM_EVENT_STA_DISCONNECTED:

        /* This is a workaround as ESP32 WiFi libs don't currently auto-reassociate. */

        esp_wifi_connect();

        xEventGroupClearBits(wifi_event_group, IPV4_GOTIP_BIT);

        break;

    default:

        break;

    }

    return ESP_OK;

}



static void initialise_wifi(void)

{

    tcpip_adapter_init();

    wifi_event_group = xEventGroupCreate();

    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) );

    ESP_ERROR_CHECK( esp_wifi_set_storage(WIFI_STORAGE_RAM) );

    wifi_config_t wifi_config = {

        .sta = {

            .ssid = EXAMPLE_WIFI_SSID,

            .password = EXAMPLE_WIFI_PASS,

        },

    };

    ESP_LOGI(TAG, "Setting WiFi configuration SSID %s...", wifi_config.sta.ssid);

    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() );

}



static void wait_for_ip()

{

    uint32_t bits = IPV4_GOTIP_BIT;



    ESP_LOGI(TAG, "Waiting for AP connection...");

    xEventGroupWaitBits(wifi_event_group, bits, false, true, portMAX_DELAY);

    ESP_LOGI(TAG, "Connected to AP");

}



static void tcp_server_task(void *pvParameters)

{

    char rx_buffer[128];

    char addr_str[128];

    int addr_family;

    int ip_protocol;



    while (1) {



        struct sockaddr_in destAddr;

        destAddr.sin_addr.s_addr = htonl(INADDR_ANY);

        destAddr.sin_family = AF_INET;

        destAddr.sin_port = htons(PORT);

        addr_family = AF_INET;

        ip_protocol = IPPROTO_IP;

        inet_ntoa_r(destAddr.sin_addr, addr_str, sizeof(addr_str) - 1);



        int listen_sock = socket(addr_family, SOCK_STREAM, ip_protocol);

        if (listen_sock < 0) {

            ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);

            break;

        }

        ESP_LOGI(TAG, "Socket created");



        int err = bind(listen_sock, (struct sockaddr *)&destAddr, sizeof(destAddr));

        if (err != 0) {

            ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);

            break;

        }

        ESP_LOGI(TAG, "Socket binded");



        err = listen(listen_sock, 1);

        if (err != 0) {

            ESP_LOGE(TAG, "Error occured during listen: errno %d", errno);

            break;

        }

        ESP_LOGI(TAG, "Socket listening");



        struct sockaddr_in6 sourceAddr; // Large enough for both IPv4 or IPv6

        uint addrLen = sizeof(sourceAddr);

        int sock = accept(listen_sock, (struct sockaddr *)&sourceAddr, &addrLen);

        if (sock < 0) {

            ESP_LOGE(TAG, "Unable to accept connection: errno %d", errno);

            break;

        }

        ESP_LOGI(TAG, "Socket accepted");



        while (1) {

            int len = recv(sock, rx_buffer, sizeof(rx_buffer) - 1, 0);

            // Error occured during receiving

            if (len < 0) {

                ESP_LOGE(TAG, "recv failed: errno %d", errno);

                break;

            }

            // Connection closed

            else if (len == 0) {

                ESP_LOGI(TAG, "Connection closed");

                break;

            }

            // Data received

            else {

                // Get the sender's ip address as string

                if (sourceAddr.sin6_family == PF_INET) {

                    inet_ntoa_r(((struct sockaddr_in *)&sourceAddr)->sin_addr.s_addr, addr_str, sizeof(addr_str) - 1);

                } else if (sourceAddr.sin6_family == PF_INET6) {

                    inet6_ntoa_r(sourceAddr.sin6_addr, addr_str, sizeof(addr_str) - 1);

                }



                rx_buffer[len] = 0; // Null-terminate whatever we received and treat like a string

                //ESP_LOGI(TAG, "Received %d bytes from %s:", len, addr_str);

                //ESP_LOGI(TAG, "%s", rx_buffer);



                int err = send(sock, rx_buffer, len, 0);

                if (err < 0) {

                    ESP_LOGE(TAG, "Error occured during sending: errno %d", errno);

                    break;

                }

            }

        }



        if (sock != -1) {

            ESP_LOGE(TAG, "Shutting down socket and restarting...");

            shutdown(sock, 0);

            close(sock);

        }

    }

    vTaskDelete(NULL);

}



void app_main()

{

    ESP_ERROR_CHECK( nvs_flash_init() );

    initialise_wifi();

    wait_for_ip();

    vTaskDelay(1000 / portTICK_PERIOD_MS);



    xTaskCreate(tcp_server_task, "tcp_server", 4096, NULL, 24, NULL);

}