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ESP32（3）UDP通信

news 来源：原创 2025/4/30 12:39:25

对于 lwIP 的 Socket 的使用方式，它与文件操作非常相似。在文件操作中，我们首先打开文件，然后进行读/写操作，最后关闭文件。在TCP/IP网络通信中，也存在着相同的操作流程，但所使用的接口不再是文件描述符或 FILE*，而是被称为 Socket 的描述符。通过 Socket，我们可以进行读、写、打开和关闭操作来进行网络数据的传输。此外，还有一些辅助函数，如查询域名/IP 地址和设置 Socket 功能等。在本章中，我们将使用 Socket 编程接口来实现 UDP 实验。

Socket 编程 UDP 连接流程

在实现 UDP协议之前，用户需要按照以下步骤配置结构体 sockaddr_in的成员变量，以便建立 UDP 连接：
①：配置 ESP32-S3 设备连接网络（必须的，因为 WiFi 是无线通信，所以需搭建通信桥梁）。
②：将 sin_family 设置为 AF_INET，表示使用 IPv4 网络协议。
③：设置 sin_port 为所需的端口号，例如 8080。
④：设置 sin_addr.s_addr 为本地 IP 地址。
⑤：调用函数 Socket 创建 Socket 连接。请注意，该函数的第二个参数指定连接类型。SOCK_STREAM 表示 TCP 连接，而 SOCK_DGRAM 表示 UDP 连接。
⑥：调用函数 bind 将本地服务器地址与 Socket 进行绑定。
⑦：调用适当的收发函数来接收或发送数据。
通过遵循这些步骤，用户可以成功地配置并建立 UDP 连接，以实现数据的发送和接收。

UDP-Server

/*
 * SPDX-FileCopyrightText: 2010-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: CC0-1.0
 */

#include <stdio.h>
#include <string.h>
#include <sys/param.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_chip_info.h"
#include "esp_eap_client.h"
#include "esp_smartconfig.h"
#include "esp_flash.h"
#include "nvs_flash.h"
#include "esp_system.h"
#include "esp_log.h"
#include "esp_event.h"
#include "esp_wifi.h"
#include "esp_netif.h"
#include "esp_mac.h"

#include "lwip/err.h"
#include "lwip/sockets.h"
#include "lwip/sys.h"
#include <lwip/netdb.h>

static const char *TAG = "network";

//=============================================================smart config===============================================================
static EventGroupHandle_t s_wifi_event_group;

static const int CONNECTED_BIT = BIT0;
static const int ESPTOUCH_DONE_BIT = BIT1;

static void smartconfig_task(void * parm);

static void event_handler(void* arg, esp_event_base_t event_base,
                                int32_t event_id, void* event_data)
{
    if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_START) {
        xTaskCreate(smartconfig_task, "smartconfig_task", 4096, NULL, 3, NULL);
    } else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        esp_wifi_connect();
        xEventGroupClearBits(s_wifi_event_group, CONNECTED_BIT);
    } else if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
        xEventGroupSetBits(s_wifi_event_group, CONNECTED_BIT);
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_SCAN_DONE) {
        ESP_LOGI(TAG, "Scan done");
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_FOUND_CHANNEL) {
        ESP_LOGI(TAG, "Found channel");
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_GOT_SSID_PSWD) {
        ESP_LOGI(TAG, "Got SSID and password");

        smartconfig_event_got_ssid_pswd_t *evt = (smartconfig_event_got_ssid_pswd_t *)event_data;
        wifi_config_t wifi_config;
        uint8_t ssid[33] = { 0 };
        uint8_t password[65] = { 0 };
        uint8_t rvd_data[33] = { 0 };

        bzero(&wifi_config, sizeof(wifi_config_t));
        memcpy(wifi_config.sta.ssid, evt->ssid, sizeof(wifi_config.sta.ssid));
        memcpy(wifi_config.sta.password, evt->password, sizeof(wifi_config.sta.password));

#ifdef CONFIG_SET_MAC_ADDRESS_OF_TARGET_AP
        wifi_config.sta.bssid_set = evt->bssid_set;
        if (wifi_config.sta.bssid_set == true) {
            ESP_LOGI(TAG, "Set MAC address of target AP: "MACSTR" ", MAC2STR(evt->bssid));
            memcpy(wifi_config.sta.bssid, evt->bssid, sizeof(wifi_config.sta.bssid));
        }
#endif

        memcpy(ssid, evt->ssid, sizeof(evt->ssid));
        memcpy(password, evt->password, sizeof(evt->password));
        ESP_LOGI(TAG, "SSID:%s", ssid);
        ESP_LOGI(TAG, "PASSWORD:%s", password);
        if (evt->type == SC_TYPE_ESPTOUCH_V2) {
            ESP_ERROR_CHECK( esp_smartconfig_get_rvd_data(rvd_data, sizeof(rvd_data)) );
            ESP_LOGI(TAG, "RVD_DATA:");
            for (int i=0; i<33; i++) {
                printf("%02x ", rvd_data[i]);
            }
            printf("\n");
        }

        ESP_ERROR_CHECK( esp_wifi_disconnect() );
        ESP_ERROR_CHECK( esp_wifi_set_config(WIFI_IF_STA, &wifi_config) );
        esp_wifi_connect();
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_SEND_ACK_DONE) {
        xEventGroupSetBits(s_wifi_event_group, ESPTOUCH_DONE_BIT);
    }
}

static void initialise_wifi(void)
{
    ESP_ERROR_CHECK(esp_netif_init());
    s_wifi_event_group = xEventGroupCreate();
    ESP_ERROR_CHECK(esp_event_loop_create_default());
    esp_netif_t *sta_netif = esp_netif_create_default_wifi_sta();
    assert(sta_netif);

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK( esp_wifi_init(&cfg) );

    ESP_ERROR_CHECK( esp_event_handler_register(WIFI_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL) );
    ESP_ERROR_CHECK( esp_event_handler_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &event_handler, NULL) );
    ESP_ERROR_CHECK( esp_event_handler_register(SC_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL) );

    ESP_ERROR_CHECK( esp_wifi_set_mode(WIFI_MODE_STA) );
    ESP_ERROR_CHECK( esp_wifi_start() );
}

static void smartconfig_task(void * parm)
{
    EventBits_t uxBits;
    ESP_ERROR_CHECK( esp_smartconfig_set_type(SC_TYPE_ESPTOUCH) );
    smartconfig_start_config_t cfg = SMARTCONFIG_START_CONFIG_DEFAULT();
    ESP_ERROR_CHECK( esp_smartconfig_start(&cfg) );
    while (1) {
        uxBits = xEventGroupWaitBits(s_wifi_event_group, CONNECTED_BIT | ESPTOUCH_DONE_BIT, true, false, portMAX_DELAY);
        if(uxBits & CONNECTED_BIT) {
            ESP_LOGI(TAG, "WiFi Connected to ap");
        }
        if(uxBits & ESPTOUCH_DONE_BIT) {
            ESP_LOGI(TAG, "smartconfig over");
            esp_smartconfig_stop();
            vTaskDelete(NULL);
        }
    }
}
//======================================================udp server=================================================================
#define PORT 8080
#define CONFIG_EXAMPLE_IPV4

static void udp_server_task(void *pvParameters)
{
    char rx_buffer[128];
    char addr_str[128];
    int addr_family = (int)pvParameters;
    int ip_protocol = 0;
    struct sockaddr_in6 dest_addr;

    while (1) {

        if (addr_family == AF_INET) {
            struct sockaddr_in *dest_addr_ip4 = (struct sockaddr_in *)&dest_addr;
            dest_addr_ip4->sin_addr.s_addr = htonl(INADDR_ANY);
            dest_addr_ip4->sin_family = AF_INET;
            dest_addr_ip4->sin_port = htons(PORT);
            ip_protocol = IPPROTO_IP;
        } else if (addr_family == AF_INET6) {
            bzero(&dest_addr.sin6_addr.un, sizeof(dest_addr.sin6_addr.un));
            dest_addr.sin6_family = AF_INET6;
            dest_addr.sin6_port = htons(PORT);
            ip_protocol = IPPROTO_IPV6;
        }

        int sock = socket(addr_family, SOCK_DGRAM, ip_protocol);
        if (sock < 0) {
            ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
            break;
        }
        ESP_LOGI(TAG, "Socket created");

#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
        int enable = 1;
        lwip_setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &enable, sizeof(enable));
#endif

#if defined(CONFIG_EXAMPLE_IPV4) && defined(CONFIG_EXAMPLE_IPV6)
        if (addr_family == AF_INET6) {
            // Note that by default IPV6 binds to both protocols, it is must be disabled
            // if both protocols used at the same time (used in CI)
            int opt = 1;
            setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
            setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &opt, sizeof(opt));
        }
#endif
        // Set timeout
        struct timeval timeout;
        timeout.tv_sec = 10;
        timeout.tv_usec = 0;
        setsockopt (sock, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof timeout);

        int err = bind(sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
        if (err < 0) {
            ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);
        }
        ESP_LOGI(TAG, "Socket bound, port %d", PORT);

        struct sockaddr_storage source_addr; // Large enough for both IPv4 or IPv6
        socklen_t socklen = sizeof(source_addr);

#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
        struct iovec iov;
        struct msghdr msg;
        struct cmsghdr *cmsgtmp;
        u8_t cmsg_buf[CMSG_SPACE(sizeof(struct in_pktinfo))];

        iov.iov_base = rx_buffer;
        iov.iov_len = sizeof(rx_buffer);
        msg.msg_control = cmsg_buf;
        msg.msg_controllen = sizeof(cmsg_buf);
        msg.msg_flags = 0;
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;
        msg.msg_name = (struct sockaddr *)&source_addr;
        msg.msg_namelen = socklen;
#endif

        while (1) {
            ESP_LOGI(TAG, "Waiting for data");
#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
            int len = recvmsg(sock, &msg, 0);
#else
            int len = recvfrom(sock, rx_buffer, sizeof(rx_buffer) - 1, 0, (struct sockaddr *)&source_addr, &socklen);
#endif
            // Error occurred during receiving
            if (len < 0) {
                ESP_LOGE(TAG, "recvfrom failed: errno %d", errno);
                break;
            }
            // Data received
            else {
                // Get the sender's ip address as string
                if (source_addr.ss_family == PF_INET) {
                    inet_ntoa_r(((struct sockaddr_in *)&source_addr)->sin_addr, addr_str, sizeof(addr_str) - 1);
#if defined(CONFIG_LWIP_NETBUF_RECVINFO) && !defined(CONFIG_EXAMPLE_IPV6)
                    for ( cmsgtmp = CMSG_FIRSTHDR(&msg); cmsgtmp != NULL; cmsgtmp = CMSG_NXTHDR(&msg, cmsgtmp) ) {
                        if ( cmsgtmp->cmsg_level == IPPROTO_IP && cmsgtmp->cmsg_type == IP_PKTINFO ) {
                            struct in_pktinfo *pktinfo;
                            pktinfo = (struct in_pktinfo*)CMSG_DATA(cmsgtmp);
                            ESP_LOGI(TAG, "dest ip: %s", inet_ntoa(pktinfo->ipi_addr));
                        }
                    }
#endif
                } else if (source_addr.ss_family == PF_INET6) {
                    inet6_ntoa_r(((struct sockaddr_in6 *)&source_addr)->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 = sendto(sock, rx_buffer, len, 0, (struct sockaddr *)&source_addr, sizeof(source_addr));
                if (err < 0) {
                    ESP_LOGE(TAG, "Error occurred 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(void)
{
    printf("Hello world!\n");

    /* Print chip information */
    esp_chip_info_t chip_info;
    uint32_t flash_size;
    esp_chip_info(&chip_info);
    printf("This is %s chip with %d CPU core(s), %s%s%s%s, ",
           CONFIG_IDF_TARGET,
           chip_info.cores,
           (chip_info.features & CHIP_FEATURE_WIFI_BGN) ? "WiFi/" : "",
           (chip_info.features & CHIP_FEATURE_BT) ? "BT" : "",
           (chip_info.features & CHIP_FEATURE_BLE) ? "BLE" : "",
           (chip_info.features & CHIP_FEATURE_IEEE802154) ? ", 802.15.4 (Zigbee/Thread)" : "");

    unsigned major_rev = chip_info.revision / 100;
    unsigned minor_rev = chip_info.revision % 100;
    printf("silicon revision v%d.%d, ", major_rev, minor_rev);
    if(esp_flash_get_size(NULL, &flash_size) != ESP_OK) {
        printf("Get flash size failed");
        return;
    }

    printf("%" PRIu32 "MB %s flash\n", flash_size / (uint32_t)(1024 * 1024),
           (chip_info.features & CHIP_FEATURE_EMB_FLASH) ? "embedded" : "external");

    printf("Minimum free heap size: %" PRIu32 " bytes\n", esp_get_minimum_free_heap_size());

    // Initialize NVS
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        ESP_ERROR_CHECK(nvs_flash_erase());
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK(ret);

    //init
    initialise_wifi();

    #ifdef CONFIG_EXAMPLE_IPV4
        xTaskCreate(udp_server_task, "udp_server", 4096, (void*)AF_INET, 5, NULL);
    #endif
    #ifdef CONFIG_EXAMPLE_IPV6
        xTaskCreate(udp_server_task, "udp_server", 4096, (void*)AF_INET6, 5, NULL);
    #endif

    while(1) {
        
        vTaskDelay(1000);
    }
}

测试：

 

使用网络调试工具创建一个UDP Client，发送数据：

UDP-Client

/*
 * SPDX-FileCopyrightText: 2010-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: CC0-1.0
 */

#include <stdio.h>
#include <string.h>
#include <sys/param.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_chip_info.h"
#include "esp_eap_client.h"
#include "esp_smartconfig.h"
#include "esp_flash.h"
#include "nvs_flash.h"
#include "esp_system.h"
#include "esp_log.h"
#include "esp_event.h"
#include "esp_wifi.h"
#include "esp_netif.h"
#include "esp_mac.h"

#include "lwip/err.h"
#include "lwip/sockets.h"
#include "lwip/sys.h"
#include <lwip/netdb.h>

static const char *TAG = "network";

//=============================================================smart config===============================================================
static EventGroupHandle_t s_wifi_event_group;

static const int CONNECTED_BIT = BIT0;
static const int ESPTOUCH_DONE_BIT = BIT1;

static void smartconfig_task(void * parm);

static void event_handler(void* arg, esp_event_base_t event_base,
                                int32_t event_id, void* event_data)
{
    if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_START) {
        xTaskCreate(smartconfig_task, "smartconfig_task", 4096, NULL, 3, NULL);
    } else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        esp_wifi_connect();
        xEventGroupClearBits(s_wifi_event_group, CONNECTED_BIT);
    } else if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
        xEventGroupSetBits(s_wifi_event_group, CONNECTED_BIT);
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_SCAN_DONE) {
        ESP_LOGI(TAG, "Scan done");
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_FOUND_CHANNEL) {
        ESP_LOGI(TAG, "Found channel");
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_GOT_SSID_PSWD) {
        ESP_LOGI(TAG, "Got SSID and password");

        smartconfig_event_got_ssid_pswd_t *evt = (smartconfig_event_got_ssid_pswd_t *)event_data;
        wifi_config_t wifi_config;
        uint8_t ssid[33] = { 0 };
        uint8_t password[65] = { 0 };
        uint8_t rvd_data[33] = { 0 };

        bzero(&wifi_config, sizeof(wifi_config_t));
        memcpy(wifi_config.sta.ssid, evt->ssid, sizeof(wifi_config.sta.ssid));
        memcpy(wifi_config.sta.password, evt->password, sizeof(wifi_config.sta.password));

#ifdef CONFIG_SET_MAC_ADDRESS_OF_TARGET_AP
        wifi_config.sta.bssid_set = evt->bssid_set;
        if (wifi_config.sta.bssid_set == true) {
            ESP_LOGI(TAG, "Set MAC address of target AP: "MACSTR" ", MAC2STR(evt->bssid));
            memcpy(wifi_config.sta.bssid, evt->bssid, sizeof(wifi_config.sta.bssid));
        }
#endif

        memcpy(ssid, evt->ssid, sizeof(evt->ssid));
        memcpy(password, evt->password, sizeof(evt->password));
        ESP_LOGI(TAG, "SSID:%s", ssid);
        ESP_LOGI(TAG, "PASSWORD:%s", password);
        if (evt->type == SC_TYPE_ESPTOUCH_V2) {
            ESP_ERROR_CHECK( esp_smartconfig_get_rvd_data(rvd_data, sizeof(rvd_data)) );
            ESP_LOGI(TAG, "RVD_DATA:");
            for (int i=0; i<33; i++) {
                printf("%02x ", rvd_data[i]);
            }
            printf("\n");
        }

        ESP_ERROR_CHECK( esp_wifi_disconnect() );
        ESP_ERROR_CHECK( esp_wifi_set_config(WIFI_IF_STA, &wifi_config) );
        esp_wifi_connect();
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_SEND_ACK_DONE) {
        xEventGroupSetBits(s_wifi_event_group, ESPTOUCH_DONE_BIT);
    }
}

static void initialise_wifi(void)
{
    ESP_ERROR_CHECK(esp_netif_init());
    s_wifi_event_group = xEventGroupCreate();
    ESP_ERROR_CHECK(esp_event_loop_create_default());
    esp_netif_t *sta_netif = esp_netif_create_default_wifi_sta();
    assert(sta_netif);

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK( esp_wifi_init(&cfg) );

    ESP_ERROR_CHECK( esp_event_handler_register(WIFI_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL) );
    ESP_ERROR_CHECK( esp_event_handler_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &event_handler, NULL) );
    ESP_ERROR_CHECK( esp_event_handler_register(SC_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL) );

    ESP_ERROR_CHECK( esp_wifi_set_mode(WIFI_MODE_STA) );
    ESP_ERROR_CHECK( esp_wifi_start() );
}

static void smartconfig_task(void * parm)
{
    EventBits_t uxBits;
    ESP_ERROR_CHECK( esp_smartconfig_set_type(SC_TYPE_ESPTOUCH) );
    smartconfig_start_config_t cfg = SMARTCONFIG_START_CONFIG_DEFAULT();
    ESP_ERROR_CHECK( esp_smartconfig_start(&cfg) );
    while (1) {
        uxBits = xEventGroupWaitBits(s_wifi_event_group, CONNECTED_BIT | ESPTOUCH_DONE_BIT, true, false, portMAX_DELAY);
        if(uxBits & CONNECTED_BIT) {
            ESP_LOGI(TAG, "WiFi Connected to ap");
        }
        if(uxBits & ESPTOUCH_DONE_BIT) {
            ESP_LOGI(TAG, "smartconfig over");
            esp_smartconfig_stop();
            vTaskDelete(NULL);
        }
    }
}
//======================================================udp client=================================================================
//#define CONFIG_EXAMPLE_SOCKET_IP_INPUT_STDIN
#define CONFIG_EXAMPLE_IPV4

#ifdef CONFIG_EXAMPLE_SOCKET_IP_INPUT_STDIN
#include "addr_from_stdin.h"
#endif

#if defined(CONFIG_EXAMPLE_IPV4)
#define HOST_IP_ADDR "192.168.4.178"
#elif defined(CONFIG_EXAMPLE_IPV6)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV6_ADDR
#else
#define HOST_IP_ADDR ""
#endif

#define PORT 8080

static const char *payload = "Message from ESP32 ";

static void udp_client_task(void *pvParameters)
{
    char rx_buffer[128];
    char host_ip[] = HOST_IP_ADDR;
    int addr_family = 0;
    int ip_protocol = 0;

    while (1) {

#if defined(CONFIG_EXAMPLE_IPV4)
        struct sockaddr_in dest_addr;
        dest_addr.sin_addr.s_addr = inet_addr(HOST_IP_ADDR);
        dest_addr.sin_family = AF_INET;
        dest_addr.sin_port = htons(PORT);
        addr_family = AF_INET;
        ip_protocol = IPPROTO_IP;
#elif defined(CONFIG_EXAMPLE_IPV6)
        struct sockaddr_in6 dest_addr = { 0 };
        inet6_aton(HOST_IP_ADDR, &dest_addr.sin6_addr);
        dest_addr.sin6_family = AF_INET6;
        dest_addr.sin6_port = htons(PORT);
        dest_addr.sin6_scope_id = esp_netif_get_netif_impl_index(EXAMPLE_INTERFACE);
        addr_family = AF_INET6;
        ip_protocol = IPPROTO_IPV6;
#elif defined(CONFIG_EXAMPLE_SOCKET_IP_INPUT_STDIN)
        struct sockaddr_storage dest_addr = { 0 };
        ESP_ERROR_CHECK(get_addr_from_stdin(PORT, SOCK_DGRAM, &ip_protocol, &addr_family, &dest_addr));
#endif

        int sock = socket(addr_family, SOCK_DGRAM, ip_protocol);
        if (sock < 0) {
            ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
            break;
        }

        // Set timeout
        struct timeval timeout;
        timeout.tv_sec = 10;
        timeout.tv_usec = 0;
        setsockopt (sock, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof timeout);

        ESP_LOGI(TAG, "Socket created, sending to %s:%d", HOST_IP_ADDR, PORT);

        while (1) {

            int err = sendto(sock, payload, strlen(payload), 0, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
            if (err < 0) {
                ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
                break;
            }
            ESP_LOGI(TAG, "Message sent");

            struct sockaddr_storage source_addr; // Large enough for both IPv4 or IPv6
            socklen_t socklen = sizeof(source_addr);
            int len = recvfrom(sock, rx_buffer, sizeof(rx_buffer) - 1, 0, (struct sockaddr *)&source_addr, &socklen);

            // Error occurred during receiving
            if (len < 0) {
                ESP_LOGE(TAG, "recvfrom failed: errno %d", errno);
                break;
            }
            // Data received
            else {
                rx_buffer[len] = 0; // Null-terminate whatever we received and treat like a string
                ESP_LOGI(TAG, "Received %d bytes from %s:", len, host_ip);
                ESP_LOGI(TAG, "%s", rx_buffer);
                if (strncmp(rx_buffer, "OK: ", 4) == 0) {
                    ESP_LOGI(TAG, "Received expected message, reconnecting");
                    break;
                }
            }

            vTaskDelay(2000 / portTICK_PERIOD_MS);
        }

        if (sock != -1) {
            ESP_LOGE(TAG, "Shutting down socket and restarting...");
            shutdown(sock, 0);
            close(sock);
        }
    }
    vTaskDelete(NULL);
}

//===================================================================================================================================

void app_main(void)
{
    printf("Hello world!\n");

    /* Print chip information */
    esp_chip_info_t chip_info;
    uint32_t flash_size;
    esp_chip_info(&chip_info);
    printf("This is %s chip with %d CPU core(s), %s%s%s%s, ",
           CONFIG_IDF_TARGET,
           chip_info.cores,
           (chip_info.features & CHIP_FEATURE_WIFI_BGN) ? "WiFi/" : "",
           (chip_info.features & CHIP_FEATURE_BT) ? "BT" : "",
           (chip_info.features & CHIP_FEATURE_BLE) ? "BLE" : "",
           (chip_info.features & CHIP_FEATURE_IEEE802154) ? ", 802.15.4 (Zigbee/Thread)" : "");

    unsigned major_rev = chip_info.revision / 100;
    unsigned minor_rev = chip_info.revision % 100;
    printf("silicon revision v%d.%d, ", major_rev, minor_rev);
    if(esp_flash_get_size(NULL, &flash_size) != ESP_OK) {
        printf("Get flash size failed");
        return;
    }

    printf("%" PRIu32 "MB %s flash\n", flash_size / (uint32_t)(1024 * 1024),
           (chip_info.features & CHIP_FEATURE_EMB_FLASH) ? "embedded" : "external");

    printf("Minimum free heap size: %" PRIu32 " bytes\n", esp_get_minimum_free_heap_size());

    // Initialize NVS
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        ESP_ERROR_CHECK(nvs_flash_erase());
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK(ret);

    //init
    initialise_wifi();

    xTaskCreate(udp_client_task, "udp_client", 4096, NULL, 5, NULL);

    while(1) {
        
        vTaskDelay(1000);
    }
}

测试：使用网络调试工具创建UDP-Server，配网后等待接收数据。

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