feat(example): Add mDNS example

examples/protocols/mdns/Makefile

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+#
+# This is a project Makefile. It is assumed the directory this Makefile resides in is a
+# project subdirectory.
+#
+
+PROJECT_NAME := mdns-test
+
+include $(IDF_PATH)/make/project.mk
+

examples/protocols/mdns/README.md

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+# mDNS example
+
+Shows how to use mDNS to advertise lookup services and hosts
+
+## Example workflow
+
+- mDNS is initialized with host name and instance name defined through `make menuconfig` and `_http._tcp` service is added to be advertised
+- WiFi STA is started and trying to connect to the access point defined through `make menuconfig`
+- The system event handler is used to pass the network events to mDNS so the service is aware when the interface comes up or down
+- GPIO0 (BOOT Button) is initialized as pulled-up input that can be monitored for button press
+- Example task is started to check if the button is pressed so it can execute the mDNS queries defined
+
+## Running the example
+
+- Run `make menuconfig` to configure the access point's SSID and Password and the default device mDNS host name and instance name
+- Run `make flash monitor` to build and upload the example to your board and connect to it's serial terminal
+- Wait for WiFi to connec to your access point
+- You can now ping the device at `[hostname].local` and browse for `_http._tcp` on the same network to find the advertised service
+- Pressing the BOOT button will start quring the local network for the predefined in `check_button` hosts and services
+
+See the README.md file in the upper level 'examples' directory for more information about examples.

examples/protocols/mdns/main/Kconfig.projbuild

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+menu "Example Configuration"
+
+config WIFI_SSID
+    string "WiFi SSID"
+	default "myssid"
+	help
+		SSID (network name) for the example to connect to.
+
+config WIFI_PASSWORD
+    string "WiFi Password"
+	default "myssid"
+	help
+		WiFi password (WPA or WPA2) for the example to use.
+
+		Can be left blank if the network has no security set.
+
+config MDNS_HOSTNAME
+    string "mDNS Hostname"
+	default "esp32-mdns"
+	help
+		mDNS Hostname for example to use
+
+config MDNS_INSTANCE
+    string "mDNS Instance Name"
+	default "ESP32 with mDNS"
+	help
+		mDNS Instance Name for example to use
+
+endmenu

examples/protocols/mdns/main/component.mk

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+#
+# "main" pseudo-component makefile.
+#
+# (Uses default behaviour of compiling all source files in directory, adding 'include' to include path.)

examples/protocols/mdns/main/mdns_example_main.c

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+/* MDNS-SD Query and advertise 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 "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 "mdns.h"
+#include "driver/gpio.h"
+#include <sys/socket.h>
+#include <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 EXAMPLE_MDNS_HOSTNAME CONFIG_MDNS_HOSTNAME
+#define EXAMPLE_MDNS_INSTANCE CONFIG_MDNS_INSTANCE
+
+/* FreeRTOS event group to signal when we are connected & ready to make a request */
+static EventGroupHandle_t wifi_event_group;
+
+/* The event group allows multiple bits for each event,
+   but we only care about one event - are we connected
+   to the AP with an IP? */
+const int IP4_CONNECTED_BIT = BIT0;
+const int IP6_CONNECTED_BIT = BIT1;
+
+static const char *TAG = "mdns-test";
+static bool auto_reconnect = true;
+
+static esp_err_t event_handler(void *ctx, system_event_t *event)
+{
+    switch(event->event_id) {
+    case SYSTEM_EVENT_STA_START:
+        esp_wifi_connect();
+        break;
+    case SYSTEM_EVENT_STA_CONNECTED:
+        /* enable ipv6 */
+        tcpip_adapter_create_ip6_linklocal(TCPIP_ADAPTER_IF_STA);
+        break;
+    case SYSTEM_EVENT_STA_GOT_IP:
+        xEventGroupSetBits(wifi_event_group, IP4_CONNECTED_BIT);
+        break;
+    case SYSTEM_EVENT_AP_STA_GOT_IP6:
+        xEventGroupSetBits(wifi_event_group, IP6_CONNECTED_BIT);
+        break;
+    case SYSTEM_EVENT_STA_DISCONNECTED:
+        /* This is a workaround as ESP32 WiFi libs don't currently
+           auto-reassociate. */
+        if (auto_reconnect) {
+            esp_wifi_connect();
+        }
+        xEventGroupClearBits(wifi_event_group, IP4_CONNECTED_BIT | IP6_CONNECTED_BIT);
+        break;
+    default:
+        break;
+    }
+    mdns_handle_system_event(ctx, event);
+    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 initialise_mdns(void)
+{
+    //initialize mDNS
+    ESP_ERROR_CHECK( mdns_init() );
+    //set mDNS hostname (required if you want to advertise services)
+    ESP_ERROR_CHECK( mdns_hostname_set(EXAMPLE_MDNS_HOSTNAME) );
+    //set default mDNS instance name
+    ESP_ERROR_CHECK( mdns_instance_name_set(EXAMPLE_MDNS_INSTANCE) );
+
+    //structure with TXT records
+    mdns_txt_item_t serviceTxtData[3] = {
+        {"board","esp32"},
+        {"u","user"},
+        {"p","password"}
+    };
+
+    //initialize service
+    ESP_ERROR_CHECK( mdns_service_add("ESP32-WebServer", "_http", "_tcp", 80, serviceTxtData, 3) );
+    //add another TXT item
+    ESP_ERROR_CHECK( mdns_service_txt_item_set("_http", "_tcp", "path", "/foobar") );
+    //change TXT item value
+    ESP_ERROR_CHECK( mdns_service_txt_item_set("_http", "_tcp", "u", "admin") );
+}
+
+static const char * if_str[] = {"STA", "AP", "ETH", "MAX"};
+static const char * ip_protocol_str[] = {"V4", "V6", "MAX"};
+
+static void mdns_print_results(mdns_result_t * results){
+    mdns_result_t * r = results;
+    mdns_ip_addr_t * a = NULL;
+    int i = 1, t;
+    while(r){
+        printf("%d: Interface: %s, Type: %s\n", i++, if_str[r->tcpip_if], ip_protocol_str[r->ip_protocol]);
+        if(r->instance_name){
+            printf("  PTR : %s\n", r->instance_name);
+        }
+        if(r->hostname){
+            printf("  SRV : %s.local:%u\n", r->hostname, r->port);
+        }
+        if(r->txt_count){
+            printf("  TXT : [%u] ", r->txt_count);
+            for(t=0; t<r->txt_count; t++){
+                printf("%s=%s; ", r->txt[t].key, r->txt[t].value);
+            }
+            printf("\n");
+        }
+        a = r->addr;
+        while(a){
+            if(a->addr.type == MDNS_IP_PROTOCOL_V6){
+                printf("  AAAA: " IPV6STR "\n", IPV62STR(a->addr.u_addr.ip6));
+            } else {
+                printf("  A   : " IPSTR "\n", IP2STR(&(a->addr.u_addr.ip4)));
+            }
+            a = a->next;
+        }
+        r = r->next;
+    }
+
+}
+
+static void query_mdns_service(const char * service_name, const char * proto)
+{
+    ESP_LOGI(TAG, "Query PTR: %s.%s.local", service_name, proto);
+
+    mdns_result_t * results = NULL;
+    esp_err_t err = mdns_query_ptr(service_name, proto, 3000, 20,  &results);
+    if(err){
+        ESP_LOGE(TAG, "Query Failed");
+        return;
+    }
+    if(!results){
+        ESP_LOGW(TAG, "No results found!");
+        return;
+    }
+
+    mdns_print_results(results);
+    mdns_query_results_free(results);
+}
+
+static void query_mdns_host(const char * host_name)
+{
+    ESP_LOGI(TAG, "Query A: %s.local", host_name);
+
+    struct ip4_addr addr;
+    addr.addr = 0;
+
+    esp_err_t err = mdns_query_a(host_name, 2000,  &addr);
+    if(err){
+        if(err == ESP_ERR_NOT_FOUND){
+            ESP_LOGW(TAG, "Host was not found!");
+            return;
+        }
+        ESP_LOGE(TAG, "Query Failed");
+        return;
+    }
+
+    ESP_LOGI(TAG, IPSTR, IP2STR(&addr));
+}
+
+static void initialise_button(void)
+{
+    gpio_config_t io_conf;
+    io_conf.intr_type = GPIO_INTR_DISABLE;
+    io_conf.pin_bit_mask = 1;
+    io_conf.mode = GPIO_MODE_INPUT;
+    io_conf.pull_up_en = 1;
+    io_conf.pull_down_en = 0;
+    gpio_config(&io_conf);
+}
+
+static void check_button(void)
+{
+    static bool old_level = true;
+    bool new_level = gpio_get_level(GPIO_NUM_0);
+    if (!new_level && old_level) {
+        query_mdns_host("esp32");
+        query_mdns_service("_arduino", "_tcp");
+        query_mdns_service("_http", "_tcp");
+        query_mdns_service("_printer", "_tcp");
+        query_mdns_service("_ipp", "_tcp");
+        query_mdns_service("_afpovertcp", "_tcp");
+        query_mdns_service("_smb", "_tcp");
+        query_mdns_service("_ftp", "_tcp");
+        query_mdns_service("_nfs", "_tcp");
+    }
+    old_level = new_level;
+}
+
+static void mdns_example_task(void *pvParameters)
+{
+    /* Wait for the callback to set the CONNECTED_BIT in the event group. */
+    xEventGroupWaitBits(wifi_event_group, IP4_CONNECTED_BIT | IP6_CONNECTED_BIT,
+                     false, true, portMAX_DELAY);
+    while(1) {
+        check_button();
+        vTaskDelay(50 / portTICK_PERIOD_MS);
+    }
+}
+
+void app_main()
+{
+    ESP_ERROR_CHECK( nvs_flash_init() );
+    initialise_mdns();
+    initialise_wifi();
+    initialise_button();
+    xTaskCreate(&mdns_example_task, "mdns_example_task", 2048, NULL, 5, NULL);
+}