Linux之通过NTP协议实现服务器时间同步的源码

Linux下通过NTP协议实现服务器时间同步（C实现）

(2009-12-09 20:59:41)


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标签： ntp linux 时间同步 杂谈

#include <stdio.h>

#include <stdlib.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <netdb.h>

#include <sys/socket.h>

#include <sys/types.h>

#include <sys/time.h>

#include <unistd.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

#define debug

//3600s*24h*(365days*70years+17days)

#define From00to70 0x83aa7e80U

#define NTPSVR1 "132.163.4.102" //USA

#define NTPSVR2 "132.163.135.132" //USA

#define NTPSVR3 "192.53.103.103" //Germany

#define NTPPORT 123

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 ntppack,newpack;

//定义为long64,解决32位数的符号位问题

long64 firsttimestamp,finaltimestamp;

long64 diftime,delaytime;

void NTP_Init()

{

bzero(&ntppack,sizeof(ntppack));

ntppack.li_vn_mode=0x1b;//0|(3<<2)|(3<<5);

//获取初始时间戳T1

firsttimestamp="From00to70"+time(NULL);//-8*3600;

ntppack.oritimestamphigh=htonl(firsttimestamp);

}

int main()

{

// ulong32 clienttime;

// ulong32 diftime,firsttimestamp,finaltimestamp;

fd_set inset1;

int32 sockfd;

struct tim tv,tv1;

struct timezone tz;

struct sockaddr_in addr;

// printf("%d,%d,%d\n",&ntppack.li_vn_mode,&ntppack.stratum,&ntppack.poll);

// printf("%d %ld\n",sizeof(NTPPacket),sizeof(ntppack));

// printf("%ld\n",time(NULL));

if((sockfd=socket(AF_INET,SOCK_DGRAM,0))<0)

{

perror("create socket error!\n");

exit(1);

}

addr.sin_family=AF_INET; //IPV4协议

addr.sin_port =htons(NTPPORT); //NTP专用的123端口

addr.sin_addr.s_addr=inet_addr(NTPSVR1); //校时服务器

bzero(&(addr.sin_zero),8); //清零

//wait 5s

tv.tv_sec=10; //select等待时间为10S

tv.tv_usec=0;

FD_ZERO(&inset1);

FD_SET(sockfd,&inset1);

NTP_Init();

//发送数据请求包

sendto(sockfd,&ntppack,sizeof(ntppack),0,(struct sockaddr *)&addr,sizeof(struct sockaddr));

//select巡视

if(select(sockfd+1,&inset1,NULL,NULL,&tv)<0)

{

perror("select error!\n");

exit(1);

}

else

{

//printf("OK\n");

if(FD_ISSET(sockfd,&inset1))

{

// printf("OK\n");

if(recv(sockfd,&newpack,sizeof(newpack),0)<0) //接收数据在newpack中。

{

perror("recv error!\n");

exit(1);

}

}

}

//到达客户机时间戳T4

finaltimestamp=time(NULL)+From00to70;//-8*3600;

//将网络上传送的大端数据改为小端形式。

newpack.root_delay= ntohl(newpack.root_delay);

newpack.root_dispersion= ntohl(newpack.root_dispersion);

newpack.reftimestamphigh=ntohl(newpack.reftimestamphigh);

newpack.reftimestamplow= ntohl(newpack.reftimestamplow);

newpack.oritimestamphigh= ntohl(newpack.oritimestamphigh);

newpack.oritimestamplow= ntohl(newpack.oritimestamplow);

newpack.recvtimestamphigh= ntohl(newpack.recvtimestamphigh);

newpack.recvtimestamplow= ntohl(newpack.recvtimestamplow);

newpack.trantimestamphigh= ntohl(newpack.trantimestamphigh);

newpack.trantimestamplow= ntohl(newpack.trantimestamplow);

//求出客户机跟服务器的时间差=((T2-T1)+(T3-T4))/2

diftime=((newpack.recvtimestamphigh-firsttimestamp)+(newpack.trantimestamphigh-finaltimestamp))>>1;

//求出延时

delaytime=((newpack.recvtimestamphigh-firsttimestamp)-(newpack.trantimestamphigh-finaltimestamp))>>1;

//diftime=(5-9)>>1;

//求出真正时间的时间戳

tv1.tv_sec=time(NULL)+diftime+delaytime;

tv1.tv_usec=0;

//tz.

#ifdef debug

printf("\n\ndebug information ...\n\n");

printf("time(NULL) is %ld\n",time(NULL));

printf("different time is %ld\n",diftime);

printf("delaytime is %ld\n",delaytime);

printf("time(NULL)+diftime+delaytime=%ld\n",time(NULL)+diftime+delaytime);

printf("tv1.tv_sec is %ld\n\n", tv1.tv_sec);

#endif

settimeofday(&tv1,NULL);

//diftime=diftime-From00to70;

#ifdef debug

//printf("different time is %ld\n",diftime);

printf("delay time is %ld\n",delaytime);

//printf("firsttimestamp is %x\n",time(NULL));

printf("newpack.tran is %ld\n",newpack.trantimestamphigh);

printf("newpack.recv is %ld\n",newpack.recvtimestamphigh);

printf("firsttimestamp is %ld\n",firsttimestamp);

printf("finaltimestamp is %ld\n",finaltimestamp);

printf("newpack.recv-firsttimestamp is %ld\n",newpack.recvtimestamphigh-firsttimestamp);

printf("newpack.tran-finaltimestamp is %ld\n",newpack.trantimestamphigh-finaltimestamp);

printf("(recv-first)+(ftran-final) is %ld\n",(newpack.recvtimestamphigh-firsttimestamp)+(newpack.trantimestamphigh-finaltimestamp));

printf("((recv-first)+(ftran-final))>>1 is %ld\n",((newpack.recvtimestamphigh-firsttimestamp)+(newpack.trantimestamphigh-finaltimestamp))>>1);

printf("different time is %ld\n\n",diftime);

printf("sizeof(long long) is:%d\n",sizeof(long long));

printf("Current time is...\n");

system("date");

#endif

}