// sntp_rapid_fire.c
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <time.h>

#define NTP_TIMESTAMP_DELTA 2208988800ull

typedef struct {
    uint8_t li_vn_mode;
    uint8_t stratum, poll;
    int8_t precision;
    uint32_t rootDelay, rootDispersion, refId;
    uint32_t refTm_s, refTm_f, origTm_s, origTm_f;
    uint32_t rxTm_s, rxTm_f, txTm_s, txTm_f;
} ntp_packet;

int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s <server_ip>\n", argv[0]);
        return 1;
    }

    int sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    struct sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_port = htons(123);
    inet_pton(AF_INET, argv[1], &server.sin_addr);

    for (int i = 0; i < 10; ++i) {
        ntp_packet pkt = {0};
        pkt.li_vn_mode = (0 << 6) | (4 << 3) | 3;

        struct timeval tv;
        gettimeofday(&tv, NULL);
        pkt.txTm_s = htonl(tv.tv_sec + NTP_TIMESTAMP_DELTA);

        sendto(sockfd, &pkt, sizeof(pkt), 0, (struct sockaddr *)&server, sizeof(server));
        printf("Request %d sent\n", i + 1);
        usleep(100000); // 100 ms
    }

    close(sockfd);
    return 0;
}