gethostbyaddr 함수 질문이 있습니다!

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <winsock2.h>
void ErrorHandling(char *message)
{ fputs(message, stderr); exit(1); }
 
int main(int argc, char *argv[])
{
	WSADATA wsaData;
	int i;
	struct hostent *host;
	SOCKADDR_IN addr;
	if(argc!=2) {
		ErrorHandling("error");
	}
	if(WSAStartup(MAKEWORD(2,2),&wsaData)!=0)
		ErrorHandling("WSAStartup() error");
 
	memset(&addr, 0, sizeof(addr));
	addr.sin_addr.s_addr=inet_addr(argv[1]);
	host=gethostbyaddr((char*)&addr.sin_addr, 4, AF_INET);
	if(!host)
		ErrorHandling("gethost error");
 
	printf("Official name: %s \n", host->h_name);
	for(i=0; host->h_aliases[i]; i++)
		printf("Aliases %d: %s \n", i+1, host->h_aliases[i]);
	printf("Address type: %s \n", 
		(host->h_addrtype==AF_INET)?"AF_INET":"AF_INET6");
	for(i=0; host->h_addr_list[i]; i++)
		printf("IP addr %d: %s \n", i+1,
			inet_ntoa(*(struct in_addr*)host->h_addr_list[i]));
	WSACleanup();
	return 0;
}