www.pudn.com > 11_code.rar > ntp.c

#include  
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#include  
struct NTPPacket 
{ 
char Leap_Ver_Mode; 
/*client=0*/ 
char Startum;  
char Poll; 
char Precision; 
double RootDelay; 
double Dispersion; 
char RefIdentifier[4]; 
char RefTimeStamp[8]; 
char OriTimeStamp[8]; 
char RecvTimeStamp[8]; 
char TransTimeStamp[8]; 
}; 
 
#define NTPPORT         123 
#define TIMEPORT        37 
#define NTPV1   "NTP/V1" 
#define NTPV2   "NTP/V2" 
#define NTPV3   "NTP/V3" 
#define NTPV4   "NTP/V4" 
#define TIME    "TIME/UDP" 
double SecondBef1970; 
struct sockaddr_in sin; 
struct addrinfo         hints, *res=NULL; 
int rc,sk; 
char Protocol[32]; 
/*构建NTP协议包*/ 
int ConstructPacket(char *Packet) 
{ 
char Version=1; 
long SecondFrom1900; 
long Zero=0; 
int Port; 
time_t timer; 
strcpy(Protocol,NTPV1); 
/*判断协议版本*/ 
if(strcmp(Protocol,NTPV1)||strcmp(Protocol,NTPV2)||strcmp(Protocol,NTPV3)||strcmp(Protocol,NTPV4)) 
{ 
	Port=NTPPORT; 
	Version=Protocol[6]-0x30; 
	Packet[0]=(Version<<3)|3;       //LI--Version--Mode 
	Packet[1]=0;            //Startum 
	Packet[2]=0;            //Poll interval 
	Packet[3]=0;            //Precision 
/*包括Root delay、Root disperse和Ref Indentifier */ 
	memset(&Packet[4],0,12); 
/*包括Ref timestamp、Ori timastamp和Receive Timestamp */ 
	memset(&Packet[16],0,24); 
	time(&timer); 
	SecondFrom1900=SecondBef1970+(long)timer; 
	SecondFrom1900=htonl(SecondFrom1900); 
	memcpy(&Packet[40],&SecondFrom1900,4); 
	memcpy(&Packet[44],&Zero,4); 
	return 48; 
	} 
else    //time/udp 
{ 
	Port=TIMEPORT; 
	memset(Packet,0,4); 
	return 4; 
	} 
return 0; 
} 
 
/*计算从1900年到现在一共有多少秒*/ 
long GetSecondFrom1900(int End) 
{ 
int Ordinal=0; 
int Run=0; 
long Result; 
int i; 
	for(i=1900;iai_addr,res->ai_addrlen))<0) 
		perror("sendto"); 
	else 
		printf("sendto success result=%d \n",result); 
	for(i=0;i<5;i++) 
	{ 
		printf("in for\n"); 
/*调用select函数，并设定超时时间为1秒*/ 
		FD_ZERO(&PendingData); 
		FD_SET(sk, &PendingData); 
		BlockTime.tv_sec=1; 
		BlockTime.tv_usec=0; 
		if(select(sk+1,&PendingData,NULL,NULL,&BlockTime)>0) 
		{ 
			FromLen=sizeof(sin); 
/*接收服务器端的信息*/ 
			if((Count=recvfrom(sk,Content,256,0,res->ai_addr,&(res->ai_addrlen)))<0) 
				perror("recvfrom"); 
			else 
				printf("recvfrom success,Count=%d \n",Count); 
			if(Protocol==TIME) 
			{ 
				memcpy(RetTime.TransTimeStamp,Content,4); 
				return 1; 
			} 
			else if(Count>=48&&Protocol!=TIME) 
			{ 
				RetTime.Leap_Ver_Mode=Content[0]; 
				RetTime.Startum=Content[1]; 
				RetTime.Poll=Content[2]; 
				RetTime.Precision=Content[3]; 
				memcpy((void *)&RetTime.RootDelay,&Content[4],4); 
				memcpy((void *)&RetTime.Dispersion,&Content[8],4); 
				memcpy((void *)RetTime.RefIdentifier,&Content[12],4); 
				memcpy((void *)RetTime.RefTimeStamp,&Content[16],8); 
				memcpy((void *)RetTime.OriTimeStamp,&Content[24],8); 
				memcpy((void *)RetTime.RecvTimeStamp,&Content[32],8); 
				memcpy((void *)RetTime.TransTimeStamp,&Content[40],8); 
				return 1; 
			} 
		} 
	} 
	close(sk); 
	return 0; 
} 
 
int main() 
{ 
	memset(&hints,0,sizeof(hints)); 
	hints.ai_family=PF_UNSPEC; 
	hints.ai_socktype=SOCK_DGRAM; 
	hints.ai_protocol=IPPROTO_UDP; 
/*调用getaddrinfo函数，获取地址信息*/ 
	rc=getaddrinfo("200.205.253.254","123",&hints,&res); 
	if (rc != 0) { 
		perror("getaddrinfo"); 
		return; 
	} 
	sk = socket(res->ai_family, res->ai_socktype,res->ai_protocol); 
	if (sk <0 ) { 
		perror("socket"); 
	} 
	else 
	{ 
		printf("socket success!\n"); 
	} 
/*调用取得NTP时间函数*/ 
	GetNtpTime(sk,res); 
}