[ESP32][esp-idf] AP+STA实现无线桥接(中转wifi信号)

引言：无线中继的主要作用是扩展WiFi信号，扩展WiFi后，令原本覆盖不到WiFi的地方也可以有WiFi，免去布线的烦恼。两个无线路由器桥接到一起，可以实现WiFi信号全覆盖。

实现的功能：WiFi模块能连接路由器，然后手机能连接WiFi模块，然后手机通过WiFi模块连接到路由器，能通过WiFi模块上网。

配置宏

# Set up wifi hotspot and share network
CONFIG_LWIP_IP_FORWARD=y
CONFIG_LWIP_IPV4_NAPT=y
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demo.c代码如下：

#include 
#include 

#include "esp_event.h"
#include "esp_log.h"
#include "esp_system.h"

#include "nvs_flash.h"
#include "esp_wifi.h"
#include "esp_netif.h"
#include "lwip/inet.h"
#include "lwip/lwip_napt.h"

// 热点名称 密码  可连接数量
#define AP_WIFI_SSID		"lisun"
#define AP_WIFI_PASS		"xjq12345"
#define AP_MAX_STA_CONN		4

// 路由器wifi名称 密码
#define STA_WIFI_SSID		"xjq"
#define STA_WIFI_PASS		"xjq12345"

static const char *TAG = "LiSun";

static esp_netif_t* _esp_netif_sta = NULL;
static esp_netif_t* _esp_netif_ap = NULL;

static void wifi_event_handler(void *arg, esp_event_base_t event_base, int32_t event_id, void *event_data) {
	if (event_id == WIFI_EVENT_AP_STACONNECTED) {
		wifi_event_ap_staconnected_t *event = (wifi_event_ap_staconnected_t *)event_data;
		ESP_LOGI(TAG, "station " MACSTR " join, AID=%d",
				 MAC2STR(event->mac), event->aid);
	} else if (event_id == WIFI_EVENT_AP_STADISCONNECTED) {
		wifi_event_ap_stadisconnected_t *event = (wifi_event_ap_stadisconnected_t *)event_data;
		ESP_LOGI(TAG, "station " MACSTR " leave, AID=%d",
				 MAC2STR(event->mac), event->aid);
	}
}

static void sta_start_handler(void* arg, esp_event_base_t event_base, int32_t event_id, void* event_data) {
	esp_wifi_connect();
}

static void got_ip_handler(void* arg, esp_event_base_t event_base, int32_t event_id, void* event_data) {
	//No need to log, wifi driver logs automatically
	esp_netif_dns_info_t dns;
	if (esp_netif_get_dns_info(_esp_netif_sta, ESP_NETIF_DNS_MAIN, &dns) == ESP_OK) {
		dhcps_dns_setserver((const ip_addr_t *)&dns.ip);
		ESP_LOGI(TAG, "set dns to:" IPSTR, IP2STR(&dns.ip.u_addr.ip4));
	}
}

static void wifi_init_softap(void)
{
	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, &wifi_event_handler, NULL));

	wifi_config_t wifi_config = {
		.ap = {
			.ssid = AP_WIFI_SSID,
			.ssid_len = strlen(AP_WIFI_SSID),
			.password = AP_WIFI_PASS,
			.max_connection = AP_MAX_STA_CONN,
			.authmode = WIFI_AUTH_WPA_WPA2_PSK
		},
	};
	if (strlen(AP_WIFI_PASS) == 0)
		wifi_config.ap.authmode = WIFI_AUTH_OPEN;

	ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_APSTA));
	ESP_ERROR_CHECK(esp_wifi_set_config(ESP_IF_WIFI_AP, &wifi_config));

	wifi_config_t cfg1 = {
		.sta = {
			.ssid = STA_WIFI_SSID,
			.password = STA_WIFI_PASS,
			.threshold = {.rssi=0, .authmode = WIFI_AUTH_WPA2_PSK},
			.pmf_cfg = {
				.capable = true,
				.required = false
			},
		},
	};
	ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &cfg1));
	ESP_ERROR_CHECK(esp_event_handler_register(WIFI_EVENT, WIFI_EVENT_STA_START, sta_start_handler, NULL));
	ESP_ERROR_CHECK(esp_wifi_start());

	esp_netif_ip_info_t ip_info;
	esp_netif_get_ip_info(esp_netif_get_handle_from_ifkey("WIFI_AP_DEF"), &ip_info);

	char ip_addr[16];
	inet_ntoa_r(ip_info.ip.addr, ip_addr, 16);
	ESP_LOGI(TAG, "Set up softAP with IP: %s", ip_addr);

	ESP_LOGI(TAG, "wifi_init_softap finished. SSID:'%s' password:'%s'", AP_WIFI_SSID, AP_WIFI_PASS);
}


void app_main(void)
{
	// Initialize networking stack
	ESP_ERROR_CHECK(esp_netif_init());

	// Create default event loop needed by the  main app
	ESP_ERROR_CHECK(esp_event_loop_create_default());

	// Initialize NVS needed by Wi-Fi
	ESP_ERROR_CHECK(nvs_flash_init());

	// Initialize Wi-Fi including netif with default config
	_esp_netif_ap = esp_netif_create_default_wifi_ap();
	_esp_netif_sta = esp_netif_create_default_wifi_sta();

	// Initialise ESP32 in SoftAP mode
	wifi_init_softap();

	ip_addr_t dnsserver;
	// Enable DNS (offer) for dhcp server
	dhcps_offer_t dhcps_dns_value = OFFER_DNS;
	dhcps_set_option_info(6, &dhcps_dns_value, sizeof(dhcps_dns_value));
	// Set custom dns server address for dhcp server 默认跟随路由器 【推荐换成国内DNS】
	dnsserver.u_addr.ip4.addr = htonl(0xC0A80301);
	dnsserver.type = IPADDR_TYPE_V4;
	dhcps_dns_setserver(&dnsserver);

#if IP_NAPT
	// !!! 必须启动sta后再设置，不然ap无网络 !!! Set to ip address of softAP netif (Default is 192.168.4.1)
	u32_t napt_netif_ip = 0xC0A80401;
	ip_napt_enable(htonl(napt_netif_ip), 1);
#endif

}

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