NTP时间校准

// TimeSyn.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <WinSock.h>
#include <TIME.H>
#pragma comment (lib,"Ws2_32")

struct   NTP_Packet
{
    int      Control_Word;
    int      root_delay;
    int      root_dispersion;
    int      reference_identifier;
    __int64    reference_timestamp;
    __int64 originate_timestamp;
    __int64 receive_timestamp;
    int      transmit_timestamp_seconds;
    int      transmit_timestamp_fractions;
};

/************************************************************************/
/* 函数说明:自动与时间服务器同步更新
/* 参数说明:无
/* 返 回 值:成功返回TRUE，失败返回FALSE
/************************************************************************/
BOOL UpdateSysTime()
{
    // 国内常用NTP服务器地址及IP
    // https://www.douban.com/note/171309770/
    WORD    wVersionRequested;
    WSADATA wsaData;

    // 初始化版本
    wVersionRequested = MAKEWORD( 1, 1 );
    if (0!=WSAStartup(wVersionRequested, &wsaData))
    {
        WSACleanup();
        return FALSE;
    }
    if (LOBYTE(wsaData.wVersion)!=1 || HIBYTE(wsaData.wVersion)!=1)
    {
        WSACleanup( );
        return FALSE;
    }

    // 这个IP是中国大陆时间同步服务器地址，可自行修改
    SOCKET soc=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
    struct sockaddr_in addrSrv;

    // ntp.sjtu.edu.cn 202.120.2.101 (上海交通大学网络中心NTP服务器地址）
    addrSrv.sin_addr.S_un.S_addr=inet_addr("202.120.2.101");
    addrSrv.sin_family=AF_INET;
    addrSrv.sin_port=htons(123);

    NTP_Packet NTP_Send,NTP_Recv;
    NTP_Send.Control_Word   =   htonl(0x0B000000);
    NTP_Send.root_delay        =   0;
    NTP_Send.root_dispersion   =   0;
    NTP_Send.reference_identifier    =   0;
    NTP_Send.reference_timestamp    =   0;
    NTP_Send.originate_timestamp    =   0;
    NTP_Send.receive_timestamp        =   0;
    NTP_Send.transmit_timestamp_seconds        =   0;
    NTP_Send.transmit_timestamp_fractions   =   0; 

    if(SOCKET_ERROR==sendto(soc,(const char*)&NTP_Send,sizeof(NTP_Send),
        0,(struct sockaddr*)&addrSrv,sizeof(addrSrv)))
    {
        closesocket(soc);
        return FALSE;
    }
    int sockaddr_Size =sizeof(addrSrv);
    if(SOCKET_ERROR==recvfrom(soc,(char*)&NTP_Recv,sizeof(NTP_Recv),
        0,(struct sockaddr*)&addrSrv,&sockaddr_Size))
    {
        closesocket(soc);
        return FALSE;
    }
    closesocket(soc);
    WSACleanup();

    SYSTEMTIME    newtime;
    float        Splitseconds;
    struct        tm    *lpLocalTime;
    time_t        ntp_time;

    // 获取时间服务器的时间
    ntp_time    = ntohl(NTP_Recv.transmit_timestamp_seconds)-2208988800;
    lpLocalTime = localtime(&ntp_time);
    if(lpLocalTime == NULL)
    {
        return FALSE;
    }

    // 获取新的时间
    newtime.wYear      =lpLocalTime->tm_year+1900;
    newtime.wMonth     =lpLocalTime->tm_mon+1;
    newtime.wDayOfWeek =lpLocalTime->tm_wday;
    newtime.wDay       =lpLocalTime->tm_mday;
    newtime.wHour      =lpLocalTime->tm_hour;
    newtime.wMinute    =lpLocalTime->tm_min;
    newtime.wSecond    =lpLocalTime->tm_sec;

    // 设置时间精度
    Splitseconds=(float)ntohl(NTP_Recv.transmit_timestamp_fractions);
    Splitseconds=(float)0.000000000200 * Splitseconds;
    Splitseconds=(float)1000.0 * Splitseconds;
    newtime.wMilliseconds   =   (unsigned   short)Splitseconds;

    // 修改本机系统时间
    SetLocalTime(&newtime);
    return TRUE;
}

int main(int argc, char* argv[])
{
    UpdateSysTime();
    return 0;
}

转自:http://blog.csdn.net/wangningyu/article/details/4522648#