关于类NTP服务器的一段代码，用于同步平台和nvr的时间。望大家不吝赐教： - #include <stdio.h>
#include <stdlib.h>
#include <WinSock2.h>
#include <time.h>
#include <stdio.h>
#define int8 char
#define uint8 unsigned char
#define uint32 unsigned int
#define ulong32 unsigned long
#define long32 long
#define int32 int
#define long64 long long
#pragma comment( lib, "ws2_32.lib")
#define NTPPORT 9966
typedef struct NTPPACKET
{
uint8 li_vn_mode;
uint8 stratum;
uint8 poll;
uint8 precision;
ulong32 root_delay;
ulong32 root_dispersion;
int8 ref_id[4];
ulong32 reftimestamphigh;
ulong32 reftimestamplow;
ulong32 oritimestamphigh;
ulong32 oritimestamplow;
ulong32 recvtimestamphigh;
ulong32 recvtimestamplow;
ulong32 trantimestamphigh;
ulong32 trantimestamplow;
}NTPPacket;
NTPPacket recvPack,sendPack;
//定义为long64,解决32位数的符号位问题
long64 recvtimestamphigh = 0,timeSpace = 0x83aa7e80U; //3600s*24h*(365days*70years+17days)
void CombineNTPPackage()
{
memset(&sendPack,0,sizeof(sendPack));
sendPack.li_vn_mode=0x1b;
recvtimestamphigh= timeSpace+time(NULL); //设置发往客户端的时间戳, 0x83aa7e80U 是1900年到1970总共的秒数，由于time(time_t *time)只能算出1970到今天的总共时间（秒） NTP时间同步报文中包含的时间是格林威治时间，是从1900年开始计算的秒数
sendPack.recvtimestamphigh = htonl(recvtimestamphigh);
}
int main()
{
WSADATA wsaData;
WORD sockVer = MAKEWORD(2, 2);
WSAStartup(sockVer, &wsaData);
int32 sockfd = -1;
struct sockaddr_in servaddr, clientAddr;
if((sockfd=socket(AF_INET,SOCK_DGRAM,0))<0){
perror("create socket error!\n");
return -1;
}
memset(&servaddr, 0,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(NTPPORT);
if(bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
perror("bind error");
return -1;
}
int ret = -1;
int len = sizeof(clientAddr);
time_t sTime,eTime;
while(1)
{
ret = recvfrom(sockfd, (char*)&recvPack, sizeof(recvPack), 0, (struct sockaddr *)&clientAddr,&len );
if(ret>0){
sTime = time(NULL);
CombineNTPPackage();
eTime = time(NULL);
sendPack.trantimestamphigh = timeSpace+eTime+eTime-sTime;
if(sendto(sockfd,(char*)&sendPack,sizeof(sendPack),0,(struct sockaddr *)&clientAddr,sizeof(struct sockaddr))<0){
perror("sendto data error!\n");
}
}else {
perror("recvfrom socket error!\n");
if(0 == ret) break;
Sleep(100);
continue;
}
Sleep(10000);
}
closesocket(sockfd);
WSACleanup( );
}
1，NTP协议算时间差： 客户机跟服务器的时间差=((T2-T1)+(T3-T4))>>1 T1是客户端的时间戳 ：recvPack.oritimestamphigh; T2是服务器自身的时间戳 ：sendPack.recvtimestamphigh T3是服务器处理过后发往客户端的时间戳 ：newpack.trantimestamphigh T4是客户端收到数据的时候的时间戳：finaltimes= time(NULL)+timeSpace - difftime=((sendPack.recvtimestamphigh-recvPack.oritimestamphigh)+(newpack.trantimestamphigh-finaltimes))>>1;
2，客户端算延时： - delaytime=((sendPack.recvtimestamphigh-recvPack.oritimestamphigh)-(sendPack.trantimestamphigh-finaltimes))>>1;
3，客户端算真正时间的时间戳： - struct timeval tv1 tv1.tv_sec=time(NULL)+difftime+delaytime;
tv1.tv_usec=0;
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