udpserver

#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <getopt.h>

#define SADDR struct sockaddr
#define SLEN sizeof(struct sockaddr_in)

int main(int argc, char *argv[]) {
    int sockfd, n;
    int port = 0;
    int  buffsize = 0;
    while (1) {
    int current_optind = optind ? optind : 1;

    static struct option options[] = {{"port", required_argument, 0, 0},
                                      {"buffsize", required_argument, 0, 0},
                                      {0, 0, 0, 0}};

    int option_index = 0;
    int c = getopt_long(argc, argv, "", options, &option_index);

    if (c == -1)
      break;

    switch (c) {
    case 0: {
      switch (option_index) {
      case 0:
        port = atoi(optarg);
        if (port < 1024 || port > 49151)
        {
            printf("Invalid port\n");
            return 1;
        }
        break;
      case 1:
        buffsize = atoi(optarg);
        if (buffsize < 1)
        {
            printf("Buffsize must be positive\n");
            return 1;
        }
        break;
      default:
        printf("Index %d is out of options\n", option_index);
      }
    } break;

    case '?':
      printf("Arguments error\n");
      break;
    default:
      fprintf(stderr, "getopt returned character code 0%o?\n", c);
    }
  }

  if (argc != 3) {
    printf("usage: client <IPaddress of server>\n");
    exit(1);
  }

  if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("socket problem");
    exit(1);
  }

  char mesg[buffsize], ipadr[16];
  struct sockaddr_in servaddr;
  struct sockaddr_in cliaddr;

  memset(&servaddr, 0, SLEN);
  servaddr.sin_family = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port = htons(port);

  if (bind(sockfd, (SADDR *)&servaddr, SLEN) < 0) {
    perror("bind problem");
    exit(1);
  }
  printf("SERVER starts...\n");

  while (1) {
    unsigned int len = SLEN;

    if ((n = recvfrom(sockfd, mesg, buffsize, 0, (SADDR *)&cliaddr, &len)) < 0) {
      perror("recvfrom");
      exit(1);
    }
    mesg[n] = 0;

    printf("REQUEST %s      FROM %s : %d\n", mesg,
           inet_ntop(AF_INET, (void *)&cliaddr.sin_addr.s_addr, ipadr, 16),
           ntohs(cliaddr.sin_port));

    if (sendto(sockfd, mesg, n, 0, (SADDR *)&cliaddr, len) < 0) {
      perror("sendto");
      exit(1);
    }
  }
}