esp32 udp组播接收程序

以下是基于ESP-IDF的ESP32 UDP组播接收程序示例：

#include <stdio.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "esp_system.h"
#include "nvs_flash.h"
#include "lwip/err.h"
#include "lwip/sys.h"
#include "lwip/sockets.h"

#define EXAMPLE_WIFI_SSID "YOUR_WIFI_SSID"
#define EXAMPLE_WIFI_PASS "YOUR_WIFI_PASSWORD"
#define EXAMPLE_MULTICAST_IPV4_ADDR "239.255.255.250"
#define EXAMPLE_MULTICAST_PORT 1900

static const char *TAG = "udp_multicast";

static void wifi_init_sta(void)
{
    tcpip_adapter_init();
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    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, "Connecting to %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());
    ESP_LOGI(TAG, "Connected to %s", wifi_config.sta.ssid);
}

void udp_receiver_task(void *pvParameters)
{
    int sockfd;
    struct sockaddr_in local_addr;
    struct sockaddr_in multicast_addr;

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        ESP_LOGE(TAG, "Failed to create socket");
        vTaskDelete(NULL);
    }

    memset(&local_addr, 0, sizeof(local_addr));
    local_addr.sin_family = AF_INET;
    local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    local_addr.sin_port = htons(EXAMPLE_MULTICAST_PORT);

    if (bind(sockfd, (struct sockaddr *)&local_addr, sizeof(local_addr)) < 0) {
        ESP_LOGE(TAG, "Failed to bind socket");
        vTaskDelete(NULL);
    }

    memset(&multicast_addr, 0, sizeof(multicast_addr));
    multicast_addr.sin_family = AF_INET;
    multicast_addr.sin_addr.s_addr = inet_addr(EXAMPLE_MULTICAST_IPV4_ADDR);
    multicast_addr.sin_port = htons(EXAMPLE_MULTICAST_PORT);

    struct ip_mreq mreq;
    mreq.imr_multiaddr.s_addr = inet_addr(EXAMPLE_MULTICAST_IPV4_ADDR);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    if (setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
        ESP_LOGE(TAG, "Failed to join multicast group");
        vTaskDelete(NULL);
    }

    char rx_buffer[128];
    while (1) {
        struct sockaddr_in source_addr;
        socklen_t socklen = sizeof(source_addr);
        int len = recvfrom(sockfd, rx_buffer, sizeof(rx_buffer) - 1, 0, (struct sockaddr *)&source_addr, &socklen);

        if (len < 0) {
            ESP_LOGE(TAG, "Failed to receive data");
            break;
        } else {
            rx_buffer[len] = 0; // Null-terminate whatever we received and treat like a string
            ESP_LOGI(TAG, "Received %d bytes from %s:%d", len, inet_ntoa(source_addr.sin_addr), ntohs(source_addr.sin_port));
            ESP_LOGI(TAG, "%s", rx_buffer);
        }
    }

    close(sockfd);
    vTaskDelete(NULL);
}

void app_main()
{
    ESP_ERROR_CHECK(nvs_flash_init());
    wifi_init_sta();

    xTaskCreate(udp_receiver_task, "udp_receiver_task", 4096, NULL, 5, NULL);
}

在这个示例中，我们首先初始化WiFi连接，然后创建一个UDP套接字并将其绑定到本地地址和端口。接下来，我们加入多播组并等待接收数据。当数据到达时，我们打印接收到的数据和来源地址和端口。