vc++ ntp client

您可以使用Windows Socket API来编写一个简单的NTP客户端，以下是一个VC++示例代码：

#include <iostream>
#include <WinSock2.h>
#include <windows.h>
#include <time.h>

#pragma comment(lib, "Ws2_32.lib")
#define NTP_TIMESTAMP_DELTA 2208988800ull

int main()
{
    // 初始化Winsock
    WSADATA wsaData;
    int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != 0) {
        std::cout << "WSAStartup failed with error: " << iResult << std::endl;
        return 1;
    }

    // 创建UDP套接字
    SOCKET sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sock == INVALID_SOCKET) {
        std::cout << "socket failed with error: " << WSAGetLastError() << std::endl;
        WSACleanup();
        return 1;
    }

    // 设置NTP服务器地址和端口
    SOCKADDR_IN serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(123);
    serverAddr.sin_addr.s_addr = inet_addr("time.nist.gov");

    // 构造NTP请求报文
    char ntpPacket[48] = {0};
    ntpPacket[0] = 0x1b;

    // 发送NTP请求
    iResult = sendto(sock, ntpPacket, sizeof(ntpPacket), 0, (SOCKADDR *)&serverAddr, sizeof(serverAddr));
    if (iResult == SOCKET_ERROR) {
        std::cout << "sendto failed with error: " << WSAGetLastError() << std::endl;
        closesocket(sock);
        WSACleanup();
        return 1;
    }

    // 接收NTP响应
    char recvBuf[1024] = {0};
    iResult = recv(sock, recvBuf, sizeof(recvBuf), 0);
    if (iResult == SOCKET_ERROR) {
        std::cout << "recv failed with error: " << WSAGetLastError() << std::endl;
        closesocket(sock);
        WSACleanup();
        return 1;
    }

    // 解析NTP响应
    unsigned long long ntpTime = 0;
    memcpy(&ntpTime, &recvBuf[40], sizeof(ntpTime));
    ntpTime = ntohl(ntpTime);
    ntpTime -= NTP_TIMESTAMP_DELTA;
    time_t unixTime = (time_t)ntpTime;
    std::cout << "Current time is " << ctime(&unixTime) << std::endl;

    // 关闭套接字并清理
    closesocket(sock);
    WSACleanup();

    return 0;
}

此代码使用了time.nist.gov作为NTP服务器，您可以根据需要更改。需要注意的是，NTP协议使用的是UTC时间，因此需要进行时区转换。