NTP timestamp

#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
 
#define NTP_SERVER  "85.114.26.194"
#define NTP_PORT    123
 
typedef struct ntp_timestamp
{
    u_int32_t seconds __attribute__ ((packed));
    u_int32_t fraction __attribute__ ((packed));
} ntp_timestamp_t;
 
typedef struct ntp_message
{
    u_int8_t status;
    u_int8_t type;
    u_int16_t precision __attribute__ ((packed));
    u_int32_t est_error __attribute__ ((packed));
    u_int32_t est_drift_rate __attribute__ ((packed));
    u_int32_t ref_clock_id __attribute__ ((packed));
 
    ntp_timestamp_t ref_timestamp;
    ntp_timestamp_t orig_timestamp;
    ntp_timestamp_t recv_timestamp;
    ntp_timestamp_t xmit_timestamp;
} ntp_message_t;
 
int main ()
{
    char buf[1520];
    int sck, scklen, cnt;
    struct in_addr ntpaddr;
    struct sockaddr_in saddr;
    u_int32_t tmstmp;
    ntp_message_t *ntp = (ntp_message_t*)buf;
 
    inet_aton (NTP_SERVER, &ntpaddr);
 
    sck = socket (AF_INET, SOCK_DGRAM, 0);
    if (sck < 0)
    {
        perror ("socket");
        exit (1);
    }
 
    saddr.sin_family = AF_INET;
    saddr.sin_port = htons (NTP_PORT);
    saddr.sin_addr.s_addr = ntpaddr.s_addr;
 
    bzero (buf, sizeof (buf));
    ntp->status = 0x08;
 
    sendto (sck, ntp, sizeof (ntp_message_t), 0, (struct sockadr *)&saddr, sizeof (saddr));
 
    while (1)
    {
        cnt = recvfrom (sck, buf, sizeof (buf), 0, (struct sockaddr *)&saddr, &scklen);
        if (cnt >= sizeof (ntp_message_t)) break;
    }
 
    tmstmp = htonl (ntp->xmit_timestamp.seconds);
 
    printf ("Timestamp: %lu\n", tmstmp);
 
    close (sck);
 
    return 0;
}

    // 66 строка
    tmstmp = htonl(ntp->xmit_timestamp.seconds) - 2208988800;
 
    // 68 строка
    printf("%s\n", ctime(&tmstmp));