ESP32學(xué)習(xí)筆記（10）——UDP客戶端

一、TCP與UDP優(yōu)缺點(diǎn)

1、TCP面向連接（如打電話要先撥號(hào)建立連接）;UDP是無(wú)連接的，即發(fā)送數(shù)據(jù)之前不需要建立連接。

2、TCP提供可靠的服務(wù)。也就是說(shuō)，通過(guò)TCP連接傳送的數(shù)據(jù)，無(wú)差錯(cuò)，不丟失，不重復(fù)，且按序到達(dá);UDP盡最大努力交付，即不保證可靠交付。
TCP通過(guò)校驗(yàn)和，重傳控制，序號(hào)標(biāo)識(shí)，滑動(dòng)窗口、確認(rèn)應(yīng)答實(shí)現(xiàn)可靠傳輸。如丟包時(shí)的重發(fā)控制，還可以對(duì)次序亂掉的分包進(jìn)行順序控制。

3、UDP具有較好的實(shí)時(shí)性，工作效率比TCP高，適用于對(duì)高速傳輸和實(shí)時(shí)性有較高的通信或廣播通信。

4、每一條TCP連接只能是點(diǎn)到點(diǎn)的;UDP支持一對(duì)一，一對(duì)多，多對(duì)一和多對(duì)多的交互通信。

5、TCP對(duì)系統(tǒng)資源要求較多，UDP對(duì)系統(tǒng)資源要求較少。

二、概述

ESP-IDF使用開源 lwIP輕量級(jí)的TCP / IP堆棧。ESP-IDF版本lwIP（esp-lwip）與上游項(xiàng)目相比有一些修改和補(bǔ)充。

ESP-IDF支持以下功能 lwIP TCP / IP堆棧功能：

BSD套接字API

BSD套接字API是一個(gè)通用的跨平臺(tái)TCP / IP套接字API，該API起源于UNIX的Berkeley標(biāo)準(zhǔn)發(fā)行版，但現(xiàn)在已在POSIX規(guī)范的一部分中進(jìn)行了標(biāo)準(zhǔn)化。BSD套接字有時(shí)稱為POSIX套接字或Berkeley套接字。

正如ESP-IDF中實(shí)施的那樣，lwIP支持BSD套接字API的所有常用用法。

ESP-IDF 編程指南——ESP-NETIF
ESP-IDF 編程指南——lwIP

三、API說(shuō)明

以下 BSD Socket 接口位于 lwip/lwip/src/include/lwip/sockets.h。

  • socket()
  • bind()
  • accept()
  • shutdown()
  • getpeername()
  • getsockopt()＆setsockopt()（請(qǐng)參閱套接字選項(xiàng)）
  • close()（通過(guò)虛擬文件系統(tǒng)組件）
  • read()，readv()，write()，writev()（經(jīng)由虛擬文件系統(tǒng)部件）
  • recv()，recvmsg()，recvfrom()
  • send()，sendmsg()，sendto()
  • select()（通過(guò)虛擬文件系統(tǒng)組件）
  • poll()（注意：在ESP-IDF上，poll()是通過(guò)內(nèi)部調(diào)用select來(lái)實(shí)現(xiàn)的，因此，select()如果有可用的方法選擇，建議直接使用。）
  • fcntl()（請(qǐng)參閱fcntl）

非標(biāo)準(zhǔn)功能：

  • ioctl()（請(qǐng)參閱ioctls）

四、UDP客戶端

4.1 主要流程

4.1.1 第一步：新建socket

int addr_family = 0;
int ip_protocol = 0;

addr_family = AF_INET;
ip_protocol = IPPROTO_IP;

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

4.1.2 第二步：配置將要連接的服務(wù)器信息（端口和IP）

服務(wù)器的地址選擇 255.255.255.255，意思是不指定局域網(wǎng)內(nèi)的某一設(shè)備，局域網(wǎng)所有的設(shè)備如果監(jiān)聽(tīng)了這個(gè)端口號(hào)，那么都可以收到esp32發(fā)來(lái)的消息。

#define HOST_IP_ADDR    "255.255.255.255"    // 要連接UDP服務(wù)器地址，默認(rèn)使用廣播
#define UDP_PORT        3333                 // 要連接UDP服務(wù)器端口號(hào)

struct sockaddr_in dest_addr;
dest_addr.sin_family = AF_INET;
dest_addr.sin_addr.s_addr = inet_addr(HOST_IP_ADDR);
dest_addr.sin_port = htons(UDP_PORT);

4.1.3 第三步：發(fā)送數(shù)據(jù)

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

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);
    close(sock);
}

4.1.4 第四步：接收數(shù)據(jù)

char rx_buffer[128];
char host_ip[] = HOST_IP_ADDR;

while(1)
{
    ······
    // 清空緩存
    memset(rx_buffer, 0, sizeof(rx_buffer));

    struct sockaddr_in source_addr; // Large enough for both IPv4 or IPv6
    socklen_t socklen = sizeof(source_addr);
    int len = recvfrom(sock, rx_buffer, sizeof(rx_buffer), 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 
    {
        ESP_LOGI(TAG, "Received %d bytes from %s:", len, host_ip);
        ESP_LOGI(TAG, "%s", rx_buffer);
    }
}
close(sock);

4.2 配置SSID和密碼連接WIFI創(chuàng)建UDP客戶端


使用 esp-idf\examples\protocols\sockets\udp_client 中的例程

/* 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.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "esp_netif.h"
#include "protocol_examples_common.h"

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

#if defined(CONFIG_EXAMPLE_IPV4)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV4_ADDR
#elif defined(CONFIG_EXAMPLE_IPV6)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV6_ADDR
#else
#define HOST_IP_ADDR ""
#endif

#define PORT CONFIG_EXAMPLE_PORT

static const char *TAG = "example";
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_in6 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;
        }
        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_in 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)
{
    ESP_ERROR_CHECK(nvs_flash_init());
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    ESP_ERROR_CHECK(example_connect());

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

idf.py menuconfig 配置服務(wù)器IP和端口


配置SSID和密碼



然后 idf.py flash 編譯下載

查看打?。?/p>


4.3 使用SmartConfig連接WIFI創(chuàng)建UDP客戶端

根據(jù) esp-idf\examples\protocols\sockets\udp_client 中的例程修改

/* 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.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "esp_netif.h"
#include "protocol_examples_common.h"

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

#include "esp_smartconfig.h"

#if defined(CONFIG_EXAMPLE_IPV4)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV4_ADDR
#elif defined(CONFIG_EXAMPLE_IPV6)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV6_ADDR
#else
#define HOST_IP_ADDR ""
#endif

#define PORT CONFIG_EXAMPLE_PORT

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

/* 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? */
static const int CONNECTED_BIT = BIT0;
static const int ESPTOUCH_DONE_BIT = BIT1;

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

static void smartconfig_example_task(void * parm);
static void udp_client_task(void *pvParameters);

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_example_task, "smartconfig_example_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 };

        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));
        wifi_config.sta.bssid_set = evt->bssid_set;
        if (wifi_config.sta.bssid_set == true) {
            memcpy(wifi_config.sta.bssid, evt->bssid, sizeof(wifi_config.sta.bssid));
        }

        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);

        ESP_ERROR_CHECK( esp_wifi_disconnect() );
        ESP_ERROR_CHECK( esp_wifi_set_config(ESP_IF_WIFI_STA, &wifi_config) );
        ESP_ERROR_CHECK( 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_example_task(void * parm)
{
    EventBits_t uxBits;
    ESP_ERROR_CHECK( esp_smartconfig_set_type(SC_TYPE_ESPTOUCH_AIRKISS) );
    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");
            xTaskCreate(udp_client_task, "udp_client", 4096, NULL, 5, NULL);
            esp_smartconfig_stop();
            vTaskDelete(NULL);
        }
    }
}

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_in6 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;
        }
        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_in 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)
{
    ESP_ERROR_CHECK(nvs_flash_init());
    initialise_wifi();
    // ESP_ERROR_CHECK(esp_netif_init());
    // ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    // ESP_ERROR_CHECK(example_connect());

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

idf.py menuconfig 配置服務(wù)器IP和端口


然后 idf.py flash 編譯下載

查看打?。?/p>


? 由 Leung 寫于 2021 年 4 月 30 日

? 參考：第十七章 ESP32的UDP廣播
　　　　樂(lè)鑫Esp32學(xué)習(xí)之旅⑧ esp32上實(shí)現(xiàn)本地 UDP 客戶端和服務(wù)端角色，在局域網(wǎng)內(nèi)實(shí)現(xiàn)通訊
　　　　ESP32 開發(fā)筆記(三）源碼示例 22_WIFI_STA_UDP 在站模式STA下實(shí)現(xiàn)UDP通訊
　　　　ESP32UDP 通信

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