#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <strings.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#include "common.h"

static const unsigned char payload_response[] = {PAYLOAD_RESPONSE};

int main() {
  unsigned char buffer[BUFSIZ];
  int listenfd;
  socklen_t len;
  struct sockaddr_in servaddr = {};
  struct sockaddr_in cliaddr;

  listenfd = socket(AF_INET, SOCK_DGRAM, 0);
  servaddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  servaddr.sin_port = htons(UDP_PORT);
  servaddr.sin_family = AF_INET;

  if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) != 0) {
    perror("udp bind");
    return 1;
  }

  size_t i;
  ssize_t n;
  for (i = 0; i < MAX_UDP_PACKETS; ++i) {
    len = sizeof(cliaddr);
    n = recvfrom(listenfd, buffer, sizeof(buffer), 0,
                 (struct sockaddr *)&cliaddr, &len);
    if (n < 0) {
      perror("udp recvfrom");
      break;
    }

    n = sendto(listenfd, payload_response, sizeof(payload_response), 0,
               (struct sockaddr *)&cliaddr, sizeof(cliaddr));
    if (n < 0) {
      perror("udp sendto");
      break;
    }
  }

  close(listenfd);

  return !(i == MAX_UDP_PACKETS);
}