C++使用套接字从URL下载文件

#include <iostream>
#include <fstream>
#include <string>
#include <winsock2.h> // Windows平台使用的套接字库

#pragma comment(lib, "ws2_32.lib") // 链接套接字库

int main() {
    std::string url = "http://example.com/file.txt";
    std::string filename = "file.txt";

    // 初始化套接字库
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        std::cerr << "Failed to initialize winsock" << std::endl;
        return -1;
    }

    // 创建套接字
    SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == INVALID_SOCKET) {
        std::cerr << "Failed to create socket" << std::endl;
        WSACleanup();
        return -1;
    }

    // 解析URL
    std::string host, path;
    int port = 80; // 默认HTTP端口
    if (url.substr(0, 7) == "http://") {
        url = url.substr(7);
        size_t pos = url.find('/');
        host = url.substr(0, pos);
        path = url.substr(pos);
    }

    // 获取主机信息
    hostent* hostInfo = gethostbyname(host.c_str());
    if (hostInfo == nullptr) {
        std::cerr << "Failed to get host information" << std::endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }

    // 构建服务器地址
    sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(port);
    serverAddr.sin_addr.s_addr = *((unsigned long*)hostInfo->h_addr);

    // 连接服务器
    if (connect(sock, (sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
        std::cerr << "Failed to connect to server" << std::endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }

    // 发送HTTP请求
    std::string request = "GET " + path + " HTTP/1.1\r\n";
    request += "Host: " + host + "\r\n";
    request += "Connection: close\r\n\r\n";
    if (send(sock, request.c_str(), request.length(), 0) == SOCKET_ERROR) {
        std::cerr << "Failed to send request" << std::endl;
        closesocket(sock);
        WSACleanup();
        return -1;
    }

    // 接收HTTP响应
    std::ofstream file(filename, std::ios::binary);
    char buffer[1024];
    int bytesRead;
    while ((bytesRead = recv(sock, buffer, sizeof(buffer), 0)) > 0) {
        file.write(buffer, bytesRead);
    }

    // 清理资源
    file.close();
    closesocket(sock);
    WSACleanup();

    std::cout << "File downloaded successfully" << std::endl;

    return 0;
}