#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define PORT 8002
#define BUFFER_SIZE 1024

int main() {
    int server_socket, client_socket;
    struct sockaddr_in server_addr, client_addr;
    char buffer[BUFFER_SIZE];
    socklen_t client_addr_len = sizeof(client_addr);

    // 创建服务器 socket
    server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket == -1) {
        perror("服务器 socket 创建失败");
        exit(EXIT_FAILURE);
    }

    // 设置 SO_REUSEADDR
    int opt = 1;
    if (setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
        perror("设置 SO_REUSEADDR 失败");
        exit(EXIT_FAILURE);
    }

    // 设置服务器地址
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(PORT);

    // 绑定服务器 socket
    if (bind(server_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        perror("绑定失败");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    // 开始监听
    if (listen(server_socket, 5) == -1) {
        perror("监听失败");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    printf("服务器已启动，等待客户端连接...\n");

    // 接受客户端连接
    client_socket = accept(server_socket, (struct sockaddr *)&client_addr, &client_addr_len);
    if (client_socket == -1) {
        perror("接受客户端连接失败");
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    printf("客户端连接成功。\n");

    // 打开文件以写入接收到的数据
    FILE *file = fopen("received_file.txt", "w");
    if (!file) {
        perror("文件打开失败");
        close(client_socket);
        close(server_socket);
        exit(EXIT_FAILURE);
    }

    // 接收分块数据
    int bytes_received;
    while ((bytes_received = recv(client_socket, buffer, BUFFER_SIZE, 0)) > 0) {
        fwrite(buffer, 1, bytes_received, file);
        printf("接收到 %d 字节数据。\n", bytes_received);
    }

    printf("文件接收完成，已保存为 received_file.txt\n");

    // 关闭文件和 socket
    fclose(file);
    close(client_socket);
    close(server_socket);

    return 0;
}