ntp c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <errno.h>
#include <endian.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>

#include <sys/wait.h>
#include <sys/time.h>

#include <netinet/in.h>

#include <pthread.h>
#include <dirent.h>
#include <fcntl.h>

#define debugprintf 1
#ifdef debugprintf
#define debugpri(mesg, args...) fprintf(stderr, "[NetRate print:%s:%d:] " mesg "\n", __FILE__, __LINE__, ##args)
#else
#define debugpri(mesg, args...)
#endif

#define JAN_1970 0x83aa7e80
#define NTPFRAC(x) (4294 * (x) + ((1981 * (x))>>11))
#define USEC(x) (((x) >> 12) - 759 * ((((x) >> 10) + 32768) >> 16))
#define Data(i) ntohl(((unsigned int *)data)[i])
#define LI 0
#define VN 3
#define MODE 3
#define STRATUM 0
#define POLL 4
#define PREC -6
struct NtpTime
{
unsigned int coarse;
unsigned int fine;
};

void sendPacket(int fd)
{
unsigned int data[12];
struct timeval now;

if (sizeof(data) != 48)
{
fprintf(stderr,"size error\n");
return;
}

memset((char*)data, 0, sizeof(data));
data[0] = htonl((LI << 30) | (VN << 27) | (MODE << 24) | (STRATUM << 16) | (POLL << 8) | (PREC & 0xff));//构造协议头部信息
data[1] = htonl(1<<16);
data[2] = htonl(1<<16);
gettimeofday(&now, NULL);
data[10] = htonl(now.tv_sec + JAN_1970);//构造传输时间戳
data[11] = htonl(NTPFRAC(now.tv_usec));
send(fd, data, 48, 0);
}

//获取NTP服务器返回的时间
void getNewTime(unsigned int *data,struct timeval *ptimeval)
{
struct NtpTime trantime;
trantime.coarse = Data(10);
trantime.fine = Data(11);

ptimeval->tv_sec = trantime.coarse - JAN_1970;
ptimeval->tv_usec = USEC(trantime.fine);
}

int getNtpTime(struct hostent* phost,struct timeval *ptimeval)
{
if(phost == NULL)
{
debugpri("err:host is null!\n");
return -1;
}
int sockfd; //socket对象
struct sockaddr_in addr_src,addr_dst;
fd_set fds;
int ret;
int recv_len;
unsigned int buf[12];
memset(buf,0,sizeof(buf));
int addr_len;
int count = 0;

struct timeval timeout;

addr_len = sizeof(struct sockaddr_in);
//本机
memset(&addr_src, 0, addr_len);
addr_src.sin_family = AF_INET;
addr_src.sin_addr.s_addr = htonl(INADDR_ANY);
addr_src.sin_port = htons(0);
//远程
memset(&addr_dst, 0, addr_len);
addr_dst.sin_family = AF_INET;
//memcpy(&(addr_dst.sin_addr.s_addr), phost->h_addr_list[0], 4);
addr_dst.sin_addr.s_addr = inet_host(210.72.145.44);
addr_dst.sin_port = htons(123);//ntp默认端口123

if(-1==(sockfd = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP)))//创建UDP socket
{
debugpri("create socket error!\n");
return -1;
}
printf("create socket ok\n");
ret = bind(sockfd, (struct sockaddr*)&addr_src, addr_len); //本地bind
if(-1==ret)
{
debugpri("bind error!\n");
close(sockfd);
return -1;
}

ret = connect(sockfd, (struct sockaddr*)&addr_dst, addr_len); //连接远程NTP服务器
if(-1==ret)
{
debugpri("connect error!\n");
close(sockfd);
return -1;
}
sendPacket(sockfd); //发送请求包
while (count < 50)//轮询请求
{
FD_ZERO(&fds);
FD_SET(sockfd, &fds);

timeout.tv_sec = 0;
timeout.tv_usec = 100000;
ret = select(sockfd + 1, &fds, NULL, NULL, &timeout);
if (0 == ret)
{
count++;
debugpri("ret == 0\n");
sendPacket(sockfd);
usleep(100*1000);
continue;
}
if(FD_ISSET(sockfd, &fds))
{
recv_len = recvfrom(sockfd, buf, sizeof(buf), 0, (struct sockaddr *)&addr_dst, (socklen_t*)&addr_len);
if(-1==recv_len)
{
debugpri("recvfrom error\n");
close(sockfd);
return -1;
}
else if(recv_len > 0)
{
debugpri("receiv data\n");
getNewTime(buf,ptimeval);
debugpri("sec = %d usec = %d",ptimeval->tv_sec ,ptimeval->tv_usec);//打印输出NTP服务器返回的时间
break;
}
}
else
{
debugpri("count %d \n",count);
usleep(50*1000);
count ++;
}
}
if(count >=50)
{
debugpri("getNewTime timeout fail \n");
close(sockfd);
return -1;
}
close(sockfd);
return 0;
}

int main(int argc, char** argv)
{
struct timeval TimeSet;
static struct hostent *host = NULL;

host = gethostbyname(argv[1]);
memset(&TimeSet ,0 ,sizeof(TimeSet));
getNtpTime(host,&TimeSet);
return 0;

}