#include
#include
#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 "lwip/err.h"
#include "lwip/sockets.h"
#include "lwip/sys.h"
#include
#define EXAMPLE_WIFI_SSID CONFIG_WIFI_SSID
#define EXAMPLE_WIFI_PASS CONFIG_WIFI_PASSWORD
#define PORT CONFIG_EXAMPLE_PORT
/ FreeRTOS event group to signal when we are connected & ready to make a request /
static EventGroupHandle_t wifi_event_group;
const int IPV4_GOTIP_BIT = BIT0;
static const char *TAG = "UDP";
static esp_err_t event_handler(void ctx, system_event_t event)
{
switch (event->event_id) {
case SYSTEM_EVENT_STA_START:
esp_wifi_connect();
ESP_LOGI(TAG, "SYSTEM_EVENT_STA_START");
break;
case SYSTEM_EVENT_STA_CONNECTED:
break;
case SYSTEM_EVENT_STA_GOT_IP:
xEventGroupSetBits(wifi_event_group, IPV4_GOTIP_BIT);
ESP_LOGI(TAG, "SYSTEM_EVENT_STA_GOT_IP");
break;
case SYSTEM_EVENT_STA_DISCONNECTED:
/ This is a workaround as ESP32 WiFi libs dont currently auto-reassociate. /
esp_wifi_connect();
xEventGroupClearBits(wifi_event_group, IPV4_GOTIP_BIT);
break;
default:
break;
}
return ESP_OK
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;
}
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 wait_for_ip()
{
uint32_t bits = IPV4_GOTIP_BIT;
ESP_LOGI(TAG, "Waiting for AP connection...");
xEventGroupWaitBits(wifi_event_group, bits, false, true, portMAX_DELAY);
ESP_LOGI(TAG, "Connected to AP");
}
static void udp_server_task(void *pvParameters)
{
char rx_buffer[4000];
char addr_str[128];
int addr_family;
int ip_protocol;
while (1) {
struct sockaddr_in destAddr;
destAddr.sin_addr.s_addr = htonl(INADDR_ANY);
destAddr.sin_family = AF_INET;
destAddr.sin_port = htons(PORT);
addr_family = AF_INET;
ip_protocol = IPPROTO_IP;
inet_ntoa_r(destAddr.sin_addr, addr_str, sizeof(addr_str) - 1);
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");
int err = bind(sock, (struct sockaddr *)&destAddr, sizeof(destAddr));
if (err < 0) {
ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);
}
ESP_LOGI(TAG, "Socket binded");
while (1) {
ESP_LOGI(TAG, "Waiting for data");
struct sockaddr_in sourceAddr;
socklen_t socklen = sizeof(sourceAddr);
int len = recvfrom(sock, rx_buffer, sizeof(rx_buffer) - 1, 0, (struct sockaddr *)&sourceAddr, &socklen);
// Error occured during receiving
if (len < 0) {
ESP_LOGE(TAG, "recvfrom failed: errno %d", errno);
break;
}
// Data received
else {
// Get the senders ip address as string
inet_ntoa_r(((struct sockaddr_in *)&sourceAddr)->sin_addr.s_addr, addr_str, sizeof(addr_str) - 1);
rx_buffer[len] = 0; // Null-terminate whatever we received and treat like a string...
總結
這次面試問的還是還是有難度的，要求當場寫代碼并且運行，也是很考察面試者寫代碼
因為Android知識體系比較龐大和復雜的，涉及到計算機知識領域的方方面面。在這里我和身邊一些朋友特意整理了一份快速進階為Android高級工程師的系統且全面的學習資料。涵蓋了Android初級——Android高級架構師進階必備的一些學習技能。
附上：我們之前因為秋招收集的二十套一二線互聯網公司Android面試真題（含BAT、小米、華為、美團、滴滴）和我自己整理Android復習筆記（包含Android基礎知識點、Android擴展知識點、Android源碼解析、設計模式匯總、Gradle知識點、常見算法題匯總。）
里面包含不同方向的自學編程路線、面試題集合/面經、及系列技術文章等，資源持續更新中…
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