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ntp_server.c
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#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#include "ntp.h"
#include "utils.h"
#define BUF_SIZE 1024
int main(int argc, char const *argv[]) {
int server = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (server < 0) {
ERROR("error opening socket%s", "");
exit(-1);
}
struct sockaddr_in serv_addr, client_addr;
memset(&client_addr, 0, sizeof(client_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(123);
if (bind(server, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
ERROR("could not bind to port %d", NTP_PORT);
exit(EXIT_FAILURE);
}
socklen_t addr_len;
int recv_len;
addr_len = sizeof(client_addr);
char buffer[BUF_SIZE] = {0};
printf("READY\r\n");
while (true) {
recv_len = recvfrom(server, buffer, BUF_SIZE, MSG_WAITALL, (struct sockaddr *)&client_addr,
&addr_len);
printf("updating NTP...\r\n");
sendto(server, buffer, recv_len, MSG_CONFIRM, (struct sockaddr *)&client_addr, addr_len);
}
shutdown(server, SHUT_RD);
return 0;
}