#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <arpa/inet.h>
#include "util.h"

const char *program_name;

void syscall_error(const char *err)
{
	perror(err);
	exit(EXIT_FAILURE);
}

void internal_error(const char *err)
{
	fprintf(stderr, "%s: %s\n", program_name, err);
	exit(EXIT_FAILURE);
}

unsigned short get_port_from_args(int argc, char **argv, int index)
{
	if (argc <= index)
		internal_error("missing port");

	unsigned int port = atoi(argv[index]);

	if (port == 0 || port > USHRT_MAX)
		internal_error("invalid port");

	return htons(port);
}