通过NTP服务器获取网络时间C++

通过NTP服务器获取网络时间

#include
#include
#include
#include
#include
#include
#include
#pragma comment (lib,"Ws2_32.lib")

#define NTP_PORT 123 /*NTP专用端口号字符串*/
#define NTP_SERVER_IP "ntp1.aliyun.com"
#define NTP_PORT_STR "123"
#define JAN_1970 0x83aa7e80 /* 1900年～1970年之间的时间秒数 */

/*
来自阿里云的 NTP 服务器：【7个】
ntp1.aliyun.com
ntp2.aliyun.com
ntp3.aliyun.com
ntp4.aliyun.com
ntp5.aliyun.com
ntp6.aliyun.com
ntp7.aliyun.com
*/

struct NTPPacket
{
union
{
struct _ControlWord
{
unsigned int uLI : 2; // 00 = no leap, clock ok
unsigned int uVersion : 3; // version 3 or version 4
unsigned int uMode : 3; // 3 for client, 4 for server, etc.
unsigned int uStratum : 8; // 0 is unspecified, 1 for primary reference system,
// 2 for next level, etc.
int nPoll : 8; // seconds as the nearest power of 2
int nPrecision : 8; // seconds to the nearest power of 2
};

int nControlWord; // 4
};

int nRootDelay; // 4
int nRootDispersion; // 4
int nReferenceIdentifier; // 4

__int64 n64ReferenceTimestamp; // 8
__int64 n64OriginateTimestamp; // 8
__int64 n64ReceiveTimestamp; // 8

int nTransmitTimestampSeconds; // 4
int nTransmitTimestampFractions; // 4
};

//获取的时间为1970年1月1日到现在的秒数
int Get_time_t(time_t & ttime)
{
ttime = 0;
WSADATA wsaData;
// Initialize Winsock
int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0) return 0;

int sockfd, rc;
addrinfo hints, *res = NULL;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
hints.ai_protocol = IPPROTO_UDP;
rc = getaddrinfo(NTP_SERVER_IP, NTP_PORT_STR, &hints, &res);

if (rc != 0) return 0;

sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (sockfd < 0) return 0;

fd_set pending_data;
timeval block_time;

int data_len = hints.ai_addrlen, count = 0, result;

NTPPacket ntpSend = { 0 };
ntpSend.nControlWord = 0x1B;
NTPPacket ntpRecv;
if ((result = sendto(sockfd, (const char*)&ntpSend, sizeof(NTPPacket), 0, hints.ai_addr, data_len)) < 0)
return 0;

FD_ZERO(&pending_data);
FD_SET(sockfd, &pending_data);

//timeout 10 sec
block_time.tv_sec = 10;
block_time.tv_usec = 0;

if (select(sockfd + 1, &pending_data, NULL, NULL, &block_time) > 0)
{
//获取的时间为1900年1月1日到现在的秒数
if ((count = recvfrom(sockfd, (char*)&ntpRecv, sizeof(NTPPacket), 0, hints.ai_addr, &data_len)) > 0)
ttime = ntohl(ntpRecv.nTransmitTimestampSeconds) - JAN_1970;
}

closesocket(sockfd);

WSACleanup();
return 1;
}