NTP协议

柔情只为你懂 2022-03-17 09:24 314阅读 0赞

网络时间协议，英文名称：Network Time Protocol（NTP）

linux C/C++实现同步NTP时间

简单的NTP客户端-C语言实现

NTP协议简介

关于下面的C++代码，我是基于博客园席纳霍霍的代码进行修改的。他的代码在我的系统里运行时间不对。非常感谢上面3位作者无私奉献。

C++ 代码：

  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <time.h>
  5. #include<iostream>
  6. #include <unistd.h>
  7. #include <sys/select.h>
  8.  #include<sys/time.h> 
  9. #include <sys/socket.h>
  10. #include <arpa/inet.h>
  11. #include <netdb.h>
  12. #include <errno.h>
  13. #include <endian.h>
  15. #define VERSION_3           3
  16. #define VERSION_4           4
  18. #define MODE_CLIENT         3
  19. #define MODE_SERVER         4
  21. #define NTP_LI              0
  22. #define NTP_VN              VERSION_3   
  23. #define NTP_MODE            MODE_CLIENT
  24. #define NTP_STRATUM         0
  25. #define NTP_POLL            4
  26. #define NTP_PRECISION       -6
  28. #define NTP_HLEN            48
  30. #define NTP_PORT            123
  31. #define NTP_SERVER          "182.92.12.11"
  33. #define TIMEOUT             10
  35. #define BUFSIZE             1500
  37. #define JAN_1970            0x83aa7e80
  39. #define NTP_CONV_FRAC32(x)  (uint64_t) ((x) * ((uint64_t)1<<32))    
  40. #define NTP_REVE_FRAC32(x)  ((double) ((double) (x) / ((uint64_t)1<<32)))   
  42. #define NTP_CONV_FRAC16(x)  (uint32_t) ((x) * ((uint32_t)1<<16))    
  43. #define NTP_REVE_FRAC16(x)  ((double)((double) (x) / ((uint32_t)1<<16)))    
  46. #define USEC2FRAC(x)        ((uint32_t) NTP_CONV_FRAC32( (x) / 1000000.0 )) 
  47. #define FRAC2USEC(x)        ((uint32_t) NTP_REVE_FRAC32( (x) * 1000000.0 )) 
  50. #define NTP_LFIXED2DOUBLE(x)    ((double) ( ntohl(((struct l_fixedpt *) (x))->intpart) - JAN_1970 + FRAC2USEC(ntohl(((struct l_fixedpt *) (x))->fracpart)) / 1000000.0 ))   
  52. using namespace std;
  53. struct s_fixedpt {
  54.     uint16_t    intpart;
  55.     uint16_t    fracpart;
  56. };
  58. struct l_fixedpt {
  59.     uint32_t    intpart;
  60.     uint32_t    fracpart;
  61. };
  64. struct ntphdr {
  65. #if __BYTE_ORDER == __BID_ENDIAN
  66.     unsigned int    ntp_li:2;
  67.     unsigned int    ntp_vn:3;
  68.     unsigned int    ntp_mode:3;
  69. #endif
  70. #if __BYTE_ORDER == __LITTLE_ENDIAN
  71.     unsigned int    ntp_mode:3;
  72.     unsigned int    ntp_vn:3;
  73.     unsigned int    ntp_li:2;
  74. #endif
  75.     uint8_t         ntp_stratum;
  76.     uint8_t         ntp_poll;
  77.     int8_t          ntp_precision;
  78.     struct s_fixedpt    ntp_rtdelay;
  79.     struct s_fixedpt    ntp_rtdispersion;
  80.     uint32_t            ntp_refid;
  81.     struct l_fixedpt    ntp_refts;
  82.     struct l_fixedpt    ntp_orits;
  83.     struct l_fixedpt    ntp_recvts;
  84.     struct l_fixedpt    ntp_transts;
  85. };
  88. in_addr_t inet_host(const char *host)
  89. {
  90.     in_addr_t saddr;
  91.     struct hostent *hostent;
  93.     if ((saddr = inet_addr(host)) == INADDR_NONE) {
  94.         if ((hostent = gethostbyname(host)) == NULL)
  95.             return INADDR_NONE;
  97.         memmove(&saddr, hostent->h_addr, hostent->h_length);
  98.     }
  100.     return saddr;
  101. }
  104. int get_ntp_packet(void *buf, size_t *size)  //构建并发送NTP请求报文
  105. {
  106.     struct ntphdr *ntp;
  107.     struct timeval tv;
  110.     if (!size || *size<NTP_HLEN)
  111.         return -1;
  113.     memset(buf, 0, *size);
  115.     ntp = (struct ntphdr *) buf;
  116.     ntp->ntp_li = NTP_LI;
  117.     ntp->ntp_vn = NTP_VN;
  118.     ntp->ntp_mode = NTP_MODE;
  119.     ntp->ntp_stratum = NTP_STRATUM;
  120.     ntp->ntp_poll = NTP_POLL;
  121.     ntp->ntp_precision = NTP_PRECISION;
  123.     gettimeofday(&tv, NULL);  //把目前的时间用tv 结构体返回
  124.     ntp->ntp_transts.intpart = htonl(tv.tv_sec + JAN_1970);
  125.     ntp->ntp_transts.fracpart = htonl(USEC2FRAC(tv.tv_usec));
  127.     *size = NTP_HLEN;
  129.     return 0;
  130. }
  134. double get_rrt(const struct ntphdr *ntp, const struct timeval *recvtv)  //往返时延
  135. {
  136.     double t1, t2, t3, t4;
  138.     t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
  139.     t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
  140.     t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
  141.     t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
  143.     return (t4 - t1) - (t3 - t2);
  144. }
  147. double get_offset(const struct ntphdr *ntp, const struct timeval *recvtv)  //偏移量
  148. {
  149.     double t1, t2, t3, t4;
  151.     t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
  152.     t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
  153.     t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
  154.     t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
  156.     return ((t2 - t1) + (t3 - t4)) / 2;
  157. }
  162. int main(int argc, char *argv[])
  163. {    
  164.     char dateBuf[64] = {0};
  165.     char cmd[128] = {0};
  166.     tm* local; 
  167.     char buf[BUFSIZE];
  168.     size_t nbytes;
  169.     int sockfd, maxfd1;
  170.     struct sockaddr_in servaddr;
  171.     fd_set readfds;
  172.     struct timeval timeout, recvtv, tv;
  173.     double offset;
  175.     // if (argc != 2) {
  176.         // usage();
  177.         // exit(-1);
  180.     servaddr.sin_family = AF_INET;
  181.     servaddr.sin_port = htons(NTP_PORT);
  182.     servaddr.sin_addr.s_addr = inet_host("119.28.183.184");
  184.     if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
  185.         perror("socket error");
  186.         exit(-1);
  187.     }
  189.     if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(struct sockaddr)) != 0) {  
  190.         perror("connect error");
  191.         exit(-1);
  192.     }
  193.     nbytes = BUFSIZE;
  194.     if (get_ntp_packet(buf, &nbytes) != 0) {
  195.         fprintf(stderr, "construct ntp request error \n");
  196.         exit(-1);
  197.     }
  198.     send(sockfd, buf, nbytes, 0);
  201.     FD_ZERO(&readfds);
  202.     FD_SET(sockfd, &readfds);
  203.     maxfd1 = sockfd + 1;
  206.     timeout.tv_sec = TIMEOUT;
  207.     timeout.tv_usec = 0;
  209.     if (select(maxfd1, &readfds, NULL, NULL, &timeout) > 0) {
  210.         if (FD_ISSET(sockfd, &readfds)) 
  211.         {
  212.             if ((nbytes = recv(sockfd, buf, BUFSIZE, 0)) < 0)  
  213.             {
  214.                 perror("recv error");
  215.                 exit(-1);
  216.             }
  218.             //计算C/S时间偏移量
  219.             gettimeofday(&recvtv, NULL);
  220.             offset = get_offset((struct ntphdr *) buf, &recvtv);    
  221.             更新系统时间
  223.             gettimeofday(&tv, NULL);
  225.             tv.tv_sec += (int) offset ;//+28800;//alen
  226.             tv.tv_usec += offset - (int) offset;
  228.             local = localtime((time_t *) &tv.tv_sec); 
  229.             strftime(dateBuf, 64, "%Y-%m-%d %H:%M:%S", local);
  230.             sprintf(cmd, "system busybox date -s \"%s\"", dateBuf);
  232.         cout << cmd <<endl;
  233.         //printf("%s\n",cmd); //alen
  235.             printf("%s \n", ctime((time_t *) &tv.tv_sec));
  238.         }
  239.     }
  241.     close(sockfd);
  243.     return 0;
  244. }

C代码：

  1. /* ntpclient.c */
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4. #include <string.h>
  5. #include <time.h>
  7. #include <unistd.h>
  8. #include <sys/select.h>
  9. #include <sys/socket.h>
  10. #include <arpa/inet.h>
  11. #include <netdb.h>
  12. #include <errno.h>
  13. #include <endian.h>
  15. #define VERSION_3           3
  16. #define VERSION_4           4
  18. #define MODE_CLIENT         3
  19. #define MODE_SERVER         4
  22. #define NTP_LI              0
  23. #define NTP_VN              VERSION_3   
  24. #define NTP_MODE            MODE_CLIENT
  25. #define NTP_STRATUM         0
  26. #define NTP_POLL            4
  27. #define NTP_PRECISION       -6
  29. #define NTP_HLEN            48
  31. #define NTP_PORT            123
  32. #define NTP_SERVER          "182.92.12.11"
  34. #define TIMEOUT             10
  36. #define BUFSIZE             1500
  38. #define JAN_1970            0x83aa7e80
  40. #define NTP_CONV_FRAC32(x)  (uint64_t) ((x) * ((uint64_t)1<<32))    
  41. #define NTP_REVE_FRAC32(x)  ((double) ((double) (x) / ((uint64_t)1<<32)))   
  43. #define NTP_CONV_FRAC16(x)  (uint32_t) ((x) * ((uint32_t)1<<16))    
  44. #define NTP_REVE_FRAC16(x)  ((double)((double) (x) / ((uint32_t)1<<16)))    
  47. #define USEC2FRAC(x)        ((uint32_t) NTP_CONV_FRAC32( (x) / 1000000.0 )) 
  48. #define FRAC2USEC(x)        ((uint32_t) NTP_REVE_FRAC32( (x) * 1000000.0 )) 
  51. #define NTP_LFIXED2DOUBLE(x)    ((double) ( ntohl(((struct l_fixedpt *) (x))->intpart) - JAN_1970 + FRAC2USEC(ntohl(((struct l_fixedpt *) (x))->fracpart)) / 1000000.0 ))   
  54. struct s_fixedpt {
  55.     uint16_t    intpart;
  56.     uint16_t    fracpart;
  57. };
  59. struct l_fixedpt {
  60.     uint32_t    intpart;
  61.     uint32_t    fracpart;
  62. };
  65. struct ntphdr {
  66. #if __BYTE_ORDER == __BID_ENDIAN
  67.     unsigned int    ntp_li:2;
  68.     unsigned int    ntp_vn:3;
  69.     unsigned int    ntp_mode:3;
  70. #endif
  71. #if __BYTE_ORDER == __LITTLE_ENDIAN
  72.     unsigned int    ntp_mode:3;
  73.     unsigned int    ntp_vn:3;
  74.     unsigned int    ntp_li:2;
  75. #endif
  76.     uint8_t         ntp_stratum;
  77.     uint8_t         ntp_poll;
  78.     int8_t          ntp_precision;
  79.     struct s_fixedpt    ntp_rtdelay;
  80.     struct s_fixedpt    ntp_rtdispersion;
  81.     uint32_t            ntp_refid;
  82.     struct l_fixedpt    ntp_refts;
  83.     struct l_fixedpt    ntp_orits;
  84.     struct l_fixedpt    ntp_recvts;
  85.     struct l_fixedpt    ntp_transts;
  86. };
  89. in_addr_t inet_host(const char *host)
  90. {
  91.     in_addr_t saddr;
  92.     struct hostent *hostent;
  94.     if ((saddr = inet_addr(host)) == INADDR_NONE) {
  95.         if ((hostent = gethostbyname(host)) == NULL)
  96.             return INADDR_NONE;
  98.         memmove(&saddr, hostent->h_addr, hostent->h_length);
  99.     }
  101.     return saddr;
  102. }
  105. int get_ntp_packet(void *buf, size_t *size)
  106. {
  107.     struct ntphdr *ntp;
  108.     struct timeval tv;
  111.     if (!size || *size<NTP_HLEN)
  112.         return -1;
  114.     memset(buf, 0, *size);
  116.     ntp = (struct ntphdr *) buf;
  117.     ntp->ntp_li = NTP_LI;
  118.     ntp->ntp_vn = NTP_VN;
  119.     ntp->ntp_mode = NTP_MODE;
  120.     ntp->ntp_stratum = NTP_STRATUM;
  121.     ntp->ntp_poll = NTP_POLL;
  122.     ntp->ntp_precision = NTP_PRECISION;
  124.     gettimeofday(&tv, NULL);
  125.     ntp->ntp_transts.intpart = htonl(tv.tv_sec + JAN_1970);
  126.     ntp->ntp_transts.fracpart = htonl(USEC2FRAC(tv.tv_usec));
  128.     *size = NTP_HLEN;
  130.     return 0;
  131. }
  134. void print_ntp(struct ntphdr *ntp)
  135. {
  136.     time_t time;
  138.     printf("LI:\t%d \n", ntp->ntp_li);
  139.     printf("VN:\t%d \n", ntp->ntp_vn);
  140.     printf("Mode:\t%d \n", ntp->ntp_mode);
  141.     printf("Stratum:\t%d \n", ntp->ntp_stratum);
  142.     printf("Poll:\t%d \n", ntp->ntp_poll);
  143.     printf("precision:\t%d \n", ntp->ntp_precision);
  145.     printf("Route delay:\t %lf \n",
  146.         ntohs(ntp->ntp_rtdelay.intpart) + NTP_REVE_FRAC16(ntohs(ntp->ntp_rtdelay.fracpart)));
  147.     printf("Route Dispersion:\t%lf \n",
  148.         ntohs(ntp->ntp_rtdispersion.intpart) + NTP_REVE_FRAC16(ntohs(ntp->ntp_rtdispersion.fracpart)));
  149.     printf("Referencd ID:\t %d \n", ntohl(ntp->ntp_refid));
  152.     time = ntohl(ntp->ntp_refts.intpart) - JAN_1970;
  153.     printf("Reference:\t%d %ld %s \n",
  154.         ntohl(ntp->ntp_refts.intpart) - JAN_1970,
  155.         FRAC2USEC(ntohl(ntp->ntp_refts.fracpart)),
  156.         ctime(&time));
  158.     time = ntohl(ntp->ntp_orits.intpart) - JAN_1970;
  159.     printf("Originate:\t%d %d frac=%ld (%s) \n",
  160.         ntohl(ntp->ntp_orits.intpart) - JAN_1970,
  161.         FRAC2USEC(ntohl(ntp->ntp_orits.fracpart)),
  162.         ntohl(ntp->ntp_orits.fracpart),
  163.         ctime(&time) );
  165.     time = ntohl(ntp->ntp_recvts.intpart) - JAN_1970;
  166.     printf("Receive:\t%d %d (%s) \n",
  167.         ntohl(ntp->ntp_recvts.intpart) - JAN_1970,
  168.         FRAC2USEC(ntohl(ntp->ntp_recvts.fracpart)),
  169.         ctime(&time) );
  171.     time = ntohl(ntp->ntp_transts.intpart) - JAN_1970;
  172.     printf("Transmit:\t%d %d (%s) \n",
  173.         ntohl(ntp->ntp_transts.intpart) - JAN_1970,
  174.         FRAC2USEC(ntohl(ntp->ntp_transts.fracpart)),
  175.         ctime(&time) );
  176. }
  179. double get_rrt(const struct ntphdr *ntp, const struct timeval *recvtv)
  180. {
  181.     double t1, t2, t3, t4;
  183.     t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
  184.     t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
  185.     t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
  186.     t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
  188.     return (t4 - t1) - (t3 - t2);
  189. }
  192. double get_offset(const struct ntphdr *ntp, const struct timeval *recvtv)
  193. {
  194.     double t1, t2, t3, t4;
  196.     t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
  197.     t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
  198.     t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
  199.     t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
  201.     return ((t2 - t1) + (t3 - t4)) / 2;
  202. }
  205. void usage(void)
  206. {
  207.     fprintf(stderr,
  208.         "Usage : ntpclient"
  209.         " destination"
  210.         "\n"
  211.     );
  212. }
  215. int main(int argc, char *argv[])
  216. {
  217.     char buf[BUFSIZE];
  218.     size_t nbytes;
  219.     int sockfd, maxfd1;
  220.     struct sockaddr_in servaddr;
  221.     fd_set readfds;
  222.     struct timeval timeout, recvtv, tv;
  223.     double offset;
  225.     if (argc != 2) {
  226.         usage();
  227.         exit(-1);
  228.     }
  231.     servaddr.sin_family = AF_INET;
  232.     servaddr.sin_port = htons(NTP_PORT);
  233.     servaddr.sin_addr.s_addr = inet_host(argv[1]);
  235.     if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
  236.         perror("socket error");
  237.         exit(-1);
  238.     }
  240.     if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(struct sockaddr)) != 0) {
  241.         perror("connect error");
  242.         exit(-1);
  243.     }
  245.     nbytes = BUFSIZE;
  246.     if (get_ntp_packet(buf, &nbytes) != 0) {
  247.         fprintf(stderr, "construct ntp request error \n");
  248.         exit(-1);
  249.     }
  250.     send(sockfd, buf, nbytes, 0);
  253.     FD_ZERO(&readfds);
  254.     FD_SET(sockfd, &readfds);
  255.     maxfd1 = sockfd + 1;
  257.     timeout.tv_sec = TIMEOUT;
  258.     timeout.tv_usec = 0;
  260.     if (select(maxfd1, &readfds, NULL, NULL, &timeout) > 0) {
  261.         if (FD_ISSET(sockfd, &readfds)) {
  262.             if ((nbytes = recv(sockfd, buf, BUFSIZE, 0)) < 0) {
  263.                 perror("recv error");
  264.                 exit(-1);
  265.             }
  267.             gettimeofday(&recvtv, NULL);
  268.             offset = get_offset((struct ntphdr *) buf, &recvtv);
  270.             gettimeofday(&tv, NULL);
  271.             tv.tv_sec += (int) offset;
  272.             tv.tv_usec += offset - (int) offset;
  274.             if (settimeofday(&tv, NULL) != 0) {
  275.                 perror("settimeofday error");
  276.                 exit(-1);
  277.             }
  278.             printf("%s \n", ctime((time_t *) &tv.tv_sec));
  279.         }
  280.     }
  282.     close(sockfd);
  284.     return 0;
  285. }

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