#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <arpa/inet.h>

#define MAGIC 0xdeadbeef

#define FLAG_FILE "flag"

#define PORT 8888

void get_flag(int client_sock) {

    FILE *file = fopen(FLAG_FILE, "r");

    if (file == NULL) {

        perror("fopen");

        return;

    }

    char flag[128];

    if (fgets(flag, sizeof(flag), file) == NULL) {

        perror("fgets");

        fclose(file);

        return;

    }

    fclose(file);

    send(client_sock, flag, strlen(flag), 0);

    close(client_sock);

}

void handle_client(int client_sock) {

    char buffer[64];

    unsigned int magic;

    unsigned int size;

    printf("client_sock: %d\n", client_sock);

    if (recv(client_sock, &magic, sizeof(magic), 0) <= 0) {

        perror("recv");

        close(client_sock);

        return;

    }

    if (magic != MAGIC) {

        printf("Invalid magic number\n");

        close(client_sock);

        return;

    }

    if (recv(client_sock, &size, 4, 0) <= 0) {

        perror("recv");

        close(client_sock);

        return;

    }

    if (recv(client_sock, buffer, size, 0) <= 0) {

        perror("recv");

        close(client_sock);

        return;

    }

    printf("Received content: %s\n", buffer);

}

 * @description

 * 实现一个服务器程序，使用 TCP 协议监听指定的端口，并处理来自客户端的连接请求。

 * 服务器会打印出 "Server listening on port XXXX"，其中 XXXX 是端口号，然后进入死循环等待客户端的连接。

 * 当有新的客户端连接时，服务器会调用 handle_client 函数处理该连接。

 * 如果发生错误，则输出相应的错误信息并退出程序。

 *

 * @param {boolean} isClientConnected

 * 表示是否已经连接到了客户端，默认为 false。

 *

 * @returns {number}

 * 返回一个整数，表示服务器监听的端口号。

 */

int main() {

    int server_sock, client_sock;

    struct sockaddr_in server_addr, client_addr;

    socklen_t client_addr_len = sizeof(client_addr);

    server_sock = socket(AF_INET, SOCK_STREAM, 0);

    if (server_sock < 0) {

        perror("socket");

        exit(EXIT_FAILURE);

    }

    server_addr.sin_family = AF_INET;

    server_addr.sin_addr.s_addr = INADDR_ANY;

    server_addr.sin_port = htons(PORT);

    if (bind(server_sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {

        perror("bind");

        close(server_sock);

        exit(EXIT_FAILURE);

    }

    if (listen(server_sock, 5) < 0) {

        perror("listen");

        close(server_sock);

        exit(EXIT_FAILURE);

    }

    printf("Server listening on port %d\n", PORT);

    while ((client_sock = accept(server_sock, (struct sockaddr *)&client_addr, &client_addr_len)) >= 0) {

        handle_client(client_sock);

    }

    close(server_sock);

    return 0;

}