NTP协议

柔情只为你懂 2022-03-17 09:24 241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][linux C_C_NTP] #

# [简单的NTP客户端-C语言实现][NTP_-C] #

[NTP协议简介][NTP]

关于下面的C++代码，我是基于博客园[席纳霍霍][Link 1]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：

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <time.h>
    #include<iostream>
    #include <unistd.h>
    #include <sys/select.h>
     #include<sys/time.h> 
    #include <sys/socket.h>
    #include <arpa/inet.h>
    #include <netdb.h>
    #include <errno.h>
    #include <endian.h>
    
    #define VERSION_3           3
    #define VERSION_4           4
    
    #define MODE_CLIENT         3
    #define MODE_SERVER         4
     
    #define NTP_LI              0
    #define NTP_VN              VERSION_3   
    #define NTP_MODE            MODE_CLIENT
    #define NTP_STRATUM         0
    #define NTP_POLL            4
    #define NTP_PRECISION       -6
    
    #define NTP_HLEN            48
    
    #define NTP_PORT            123
    #define NTP_SERVER          "182.92.12.11"
    
    #define TIMEOUT             10
    
    #define BUFSIZE             1500
    
    #define JAN_1970            0x83aa7e80
    
    #define NTP_CONV_FRAC32(x)  (uint64_t) ((x) * ((uint64_t)1<<32))    
    #define NTP_REVE_FRAC32(x)  ((double) ((double) (x) / ((uint64_t)1<<32)))   
    
    #define NTP_CONV_FRAC16(x)  (uint32_t) ((x) * ((uint32_t)1<<16))    
    #define NTP_REVE_FRAC16(x)  ((double)((double) (x) / ((uint32_t)1<<16)))    
    
    
    #define USEC2FRAC(x)        ((uint32_t) NTP_CONV_FRAC32( (x) / 1000000.0 )) 
    #define FRAC2USEC(x)        ((uint32_t) NTP_REVE_FRAC32( (x) * 1000000.0 )) 
    
    
    #define NTP_LFIXED2DOUBLE(x)    ((double) ( ntohl(((struct l_fixedpt *) (x))->intpart) - JAN_1970 + FRAC2USEC(ntohl(((struct l_fixedpt *) (x))->fracpart)) / 1000000.0 ))   
    
    using namespace std;
    struct s_fixedpt {
        uint16_t    intpart;
        uint16_t    fracpart;
    };
    
    struct l_fixedpt {
        uint32_t    intpart;
        uint32_t    fracpart;
    };
    
    
    struct ntphdr {
    #if __BYTE_ORDER == __BID_ENDIAN
        unsigned int    ntp_li:2;
        unsigned int    ntp_vn:3;
        unsigned int    ntp_mode:3;
    #endif
    #if __BYTE_ORDER == __LITTLE_ENDIAN
        unsigned int    ntp_mode:3;
        unsigned int    ntp_vn:3;
        unsigned int    ntp_li:2;
    #endif
        uint8_t         ntp_stratum;
        uint8_t         ntp_poll;
        int8_t          ntp_precision;
        struct s_fixedpt    ntp_rtdelay;
        struct s_fixedpt    ntp_rtdispersion;
        uint32_t            ntp_refid;
        struct l_fixedpt    ntp_refts;
        struct l_fixedpt    ntp_orits;
        struct l_fixedpt    ntp_recvts;
        struct l_fixedpt    ntp_transts;
    };
    
    
    in_addr_t inet_host(const char *host)
    {
        in_addr_t saddr;
        struct hostent *hostent;
    
        if ((saddr = inet_addr(host)) == INADDR_NONE) {
            if ((hostent = gethostbyname(host)) == NULL)
                return INADDR_NONE;
    
            memmove(&saddr, hostent->h_addr, hostent->h_length);
        }
    
        return saddr;
    }
    
    
    int get_ntp_packet(void *buf, size_t *size)  //构建并发送NTP请求报文
    {
        struct ntphdr *ntp;
        struct timeval tv;
    
    
        if (!size || *size<NTP_HLEN)
            return -1;
    
        memset(buf, 0, *size);
    
        ntp = (struct ntphdr *) buf;
        ntp->ntp_li = NTP_LI;
        ntp->ntp_vn = NTP_VN;
        ntp->ntp_mode = NTP_MODE;
        ntp->ntp_stratum = NTP_STRATUM;
        ntp->ntp_poll = NTP_POLL;
        ntp->ntp_precision = NTP_PRECISION;
    
        gettimeofday(&tv, NULL);  //把目前的时间用tv 结构体返回
        ntp->ntp_transts.intpart = htonl(tv.tv_sec + JAN_1970);
        ntp->ntp_transts.fracpart = htonl(USEC2FRAC(tv.tv_usec));
    
        *size = NTP_HLEN;
    
        return 0;
    }
    
    
    
    double get_rrt(const struct ntphdr *ntp, const struct timeval *recvtv)  //往返时延
    {
        double t1, t2, t3, t4;
    
        t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
        t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
        t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
        t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
    
        return (t4 - t1) - (t3 - t2);
    }
    
    
    double get_offset(const struct ntphdr *ntp, const struct timeval *recvtv)  //偏移量
    {
        double t1, t2, t3, t4;
    
        t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
        t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
        t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
        t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
    
        return ((t2 - t1) + (t3 - t4)) / 2;
    }
    
    
    
    
    int main(int argc, char *argv[])
    {    
        char dateBuf[64] = {0};
        char cmd[128] = {0};
        tm* local; 
        char buf[BUFSIZE];
        size_t nbytes;
        int sockfd, maxfd1;
        struct sockaddr_in servaddr;
        fd_set readfds;
        struct timeval timeout, recvtv, tv;
        double offset;
    
        // if (argc != 2) {
            // usage();
            // exit(-1);
       
    
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(NTP_PORT);
        servaddr.sin_addr.s_addr = inet_host("119.28.183.184");
        
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
            perror("socket error");
            exit(-1);
        }
    
        if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(struct sockaddr)) != 0) {  
            perror("connect error");
            exit(-1);
        }
        nbytes = BUFSIZE;
        if (get_ntp_packet(buf, &nbytes) != 0) {
            fprintf(stderr, "construct ntp request error \n");
            exit(-1);
        }
        send(sockfd, buf, nbytes, 0);
    
    
        FD_ZERO(&readfds);
        FD_SET(sockfd, &readfds);
        maxfd1 = sockfd + 1;
    
    
        timeout.tv_sec = TIMEOUT;
        timeout.tv_usec = 0;
        
        if (select(maxfd1, &readfds, NULL, NULL, &timeout) > 0) {
            if (FD_ISSET(sockfd, &readfds)) 
            {
                if ((nbytes = recv(sockfd, buf, BUFSIZE, 0)) < 0)  
                {
                    perror("recv error");
                    exit(-1);
                }
                
                //计算C/S时间偏移量
                gettimeofday(&recvtv, NULL);
                offset = get_offset((struct ntphdr *) buf, &recvtv);    
                更新系统时间
    
                gettimeofday(&tv, NULL);
                
                tv.tv_sec += (int) offset ;//+28800;//alen
                tv.tv_usec += offset - (int) offset;
                
                local = localtime((time_t *) &tv.tv_sec); 
                strftime(dateBuf, 64, "%Y-%m-%d %H:%M:%S", local);
                sprintf(cmd, "system busybox date -s \"%s\"", dateBuf);
    
    	    cout << cmd <<endl;
    	    //printf("%s\n",cmd); //alen
                
                printf("%s \n", ctime((time_t *) &tv.tv_sec));
                
    
            }
        }
    
        close(sockfd);
    
        return 0;
    }

C代码：

/* ntpclient.c */
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <time.h>
    
    #include <unistd.h>
    #include <sys/select.h>
    #include <sys/socket.h>
    #include <arpa/inet.h>
    #include <netdb.h>
    #include <errno.h>
    #include <endian.h>
    
    #define VERSION_3           3
    #define VERSION_4           4
    
    #define MODE_CLIENT         3
    #define MODE_SERVER         4
    
    
    #define NTP_LI              0
    #define NTP_VN              VERSION_3   
    #define NTP_MODE            MODE_CLIENT
    #define NTP_STRATUM         0
    #define NTP_POLL            4
    #define NTP_PRECISION       -6
    
    #define NTP_HLEN            48
    
    #define NTP_PORT            123
    #define NTP_SERVER          "182.92.12.11"
    
    #define TIMEOUT             10
    
    #define BUFSIZE             1500
    
    #define JAN_1970            0x83aa7e80
    
    #define NTP_CONV_FRAC32(x)  (uint64_t) ((x) * ((uint64_t)1<<32))    
    #define NTP_REVE_FRAC32(x)  ((double) ((double) (x) / ((uint64_t)1<<32)))   
    
    #define NTP_CONV_FRAC16(x)  (uint32_t) ((x) * ((uint32_t)1<<16))    
    #define NTP_REVE_FRAC16(x)  ((double)((double) (x) / ((uint32_t)1<<16)))    
    
    
    #define USEC2FRAC(x)        ((uint32_t) NTP_CONV_FRAC32( (x) / 1000000.0 )) 
    #define FRAC2USEC(x)        ((uint32_t) NTP_REVE_FRAC32( (x) * 1000000.0 )) 
    
    
    #define NTP_LFIXED2DOUBLE(x)    ((double) ( ntohl(((struct l_fixedpt *) (x))->intpart) - JAN_1970 + FRAC2USEC(ntohl(((struct l_fixedpt *) (x))->fracpart)) / 1000000.0 ))   
    
    
    struct s_fixedpt {
        uint16_t    intpart;
        uint16_t    fracpart;
    };
    
    struct l_fixedpt {
        uint32_t    intpart;
        uint32_t    fracpart;
    };
    
    
    struct ntphdr {
    #if __BYTE_ORDER == __BID_ENDIAN
        unsigned int    ntp_li:2;
        unsigned int    ntp_vn:3;
        unsigned int    ntp_mode:3;
    #endif
    #if __BYTE_ORDER == __LITTLE_ENDIAN
        unsigned int    ntp_mode:3;
        unsigned int    ntp_vn:3;
        unsigned int    ntp_li:2;
    #endif
        uint8_t         ntp_stratum;
        uint8_t         ntp_poll;
        int8_t          ntp_precision;
        struct s_fixedpt    ntp_rtdelay;
        struct s_fixedpt    ntp_rtdispersion;
        uint32_t            ntp_refid;
        struct l_fixedpt    ntp_refts;
        struct l_fixedpt    ntp_orits;
        struct l_fixedpt    ntp_recvts;
        struct l_fixedpt    ntp_transts;
    };
    
    
    in_addr_t inet_host(const char *host)
    {
        in_addr_t saddr;
        struct hostent *hostent;
    
        if ((saddr = inet_addr(host)) == INADDR_NONE) {
            if ((hostent = gethostbyname(host)) == NULL)
                return INADDR_NONE;
    
            memmove(&saddr, hostent->h_addr, hostent->h_length);
        }
    
        return saddr;
    }
    
    
    int get_ntp_packet(void *buf, size_t *size)
    {
        struct ntphdr *ntp;
        struct timeval tv;
    
    
        if (!size || *size<NTP_HLEN)
            return -1;
    
        memset(buf, 0, *size);
    
        ntp = (struct ntphdr *) buf;
        ntp->ntp_li = NTP_LI;
        ntp->ntp_vn = NTP_VN;
        ntp->ntp_mode = NTP_MODE;
        ntp->ntp_stratum = NTP_STRATUM;
        ntp->ntp_poll = NTP_POLL;
        ntp->ntp_precision = NTP_PRECISION;
    
        gettimeofday(&tv, NULL);
        ntp->ntp_transts.intpart = htonl(tv.tv_sec + JAN_1970);
        ntp->ntp_transts.fracpart = htonl(USEC2FRAC(tv.tv_usec));
    
        *size = NTP_HLEN;
    
        return 0;
    }
    
    
    void print_ntp(struct ntphdr *ntp)
    {
        time_t time;
    
        printf("LI:\t%d \n", ntp->ntp_li);
        printf("VN:\t%d \n", ntp->ntp_vn);
        printf("Mode:\t%d \n", ntp->ntp_mode);
        printf("Stratum:\t%d \n", ntp->ntp_stratum);
        printf("Poll:\t%d \n", ntp->ntp_poll);
        printf("precision:\t%d \n", ntp->ntp_precision);
    
        printf("Route delay:\t %lf \n",
            ntohs(ntp->ntp_rtdelay.intpart) + NTP_REVE_FRAC16(ntohs(ntp->ntp_rtdelay.fracpart)));
        printf("Route Dispersion:\t%lf \n",
            ntohs(ntp->ntp_rtdispersion.intpart) + NTP_REVE_FRAC16(ntohs(ntp->ntp_rtdispersion.fracpart)));
        printf("Referencd ID:\t %d \n", ntohl(ntp->ntp_refid));
    
    
        time = ntohl(ntp->ntp_refts.intpart) - JAN_1970;
        printf("Reference:\t%d %ld %s \n",
            ntohl(ntp->ntp_refts.intpart) - JAN_1970,
            FRAC2USEC(ntohl(ntp->ntp_refts.fracpart)),
            ctime(&time));
    
        time = ntohl(ntp->ntp_orits.intpart) - JAN_1970;
        printf("Originate:\t%d %d frac=%ld (%s) \n",
            ntohl(ntp->ntp_orits.intpart) - JAN_1970,
            FRAC2USEC(ntohl(ntp->ntp_orits.fracpart)),
            ntohl(ntp->ntp_orits.fracpart),
            ctime(&time) );
    
        time = ntohl(ntp->ntp_recvts.intpart) - JAN_1970;
        printf("Receive:\t%d %d (%s) \n",
            ntohl(ntp->ntp_recvts.intpart) - JAN_1970,
            FRAC2USEC(ntohl(ntp->ntp_recvts.fracpart)),
            ctime(&time) );
    
        time = ntohl(ntp->ntp_transts.intpart) - JAN_1970;
        printf("Transmit:\t%d %d (%s) \n",
            ntohl(ntp->ntp_transts.intpart) - JAN_1970,
            FRAC2USEC(ntohl(ntp->ntp_transts.fracpart)),
            ctime(&time) );
    }
    
    
    double get_rrt(const struct ntphdr *ntp, const struct timeval *recvtv)
    {
        double t1, t2, t3, t4;
    
        t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
        t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
        t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
        t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
    
        return (t4 - t1) - (t3 - t2);
    }
    
    
    double get_offset(const struct ntphdr *ntp, const struct timeval *recvtv)
    {
        double t1, t2, t3, t4;
    
        t1 = NTP_LFIXED2DOUBLE(&ntp->ntp_orits);
        t2 = NTP_LFIXED2DOUBLE(&ntp->ntp_recvts);
        t3 = NTP_LFIXED2DOUBLE(&ntp->ntp_transts);
        t4 = recvtv->tv_sec + recvtv->tv_usec / 1000000.0;
    
        return ((t2 - t1) + (t3 - t4)) / 2;
    }
    
    
    void usage(void)
    {
        fprintf(stderr,
            "Usage : ntpclient"
            " destination"
            "\n"
        );
    }
    
    
    int main(int argc, char *argv[])
    {
        char buf[BUFSIZE];
        size_t nbytes;
        int sockfd, maxfd1;
        struct sockaddr_in servaddr;
        fd_set readfds;
        struct timeval timeout, recvtv, tv;
        double offset;
    
        if (argc != 2) {
            usage();
            exit(-1);
        }
    
    
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(NTP_PORT);
        servaddr.sin_addr.s_addr = inet_host(argv[1]);
    
        if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
            perror("socket error");
            exit(-1);
        }
    
        if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(struct sockaddr)) != 0) {
            perror("connect error");
            exit(-1);
        }
    
        nbytes = BUFSIZE;
        if (get_ntp_packet(buf, &nbytes) != 0) {
            fprintf(stderr, "construct ntp request error \n");
            exit(-1);
        }
        send(sockfd, buf, nbytes, 0);
    
    
        FD_ZERO(&readfds);
        FD_SET(sockfd, &readfds);
        maxfd1 = sockfd + 1;
    
        timeout.tv_sec = TIMEOUT;
        timeout.tv_usec = 0;
    
        if (select(maxfd1, &readfds, NULL, NULL, &timeout) > 0) {
            if (FD_ISSET(sockfd, &readfds)) {
                if ((nbytes = recv(sockfd, buf, BUFSIZE, 0)) < 0) {
                    perror("recv error");
                    exit(-1);
                }
    
                gettimeofday(&recvtv, NULL);
                offset = get_offset((struct ntphdr *) buf, &recvtv);
    
                gettimeofday(&tv, NULL);
                tv.tv_sec += (int) offset;
                tv.tv_usec += offset - (int) offset;
    
                if (settimeofday(&tv, NULL) != 0) {
                    perror("settimeofday error");
                    exit(-1);
                }
                printf("%s \n", ctime((time_t *) &tv.tv_sec));
            }
        }
    
        close(sockfd);
    
        return 0;
    }

[linux C_C_NTP]: https://www.cnblogs.com/zy791976083/p/9779421.html
[NTP_-C]: https://blog.csdn.net/C3080844491/article/details/77934050?skintest=skin3-template-test
[NTP]: https://wenku.baidu.com/view/867ae3c40c22590102029d84.html
[Link 1]: https://www.cnblogs.com/zy791976083/