linux socket programming

gethostbyname.cc

#include <cstring> //memset
#include <sys/socket.h>
#include <netdb.h>	//hostent
#include <arpa/inet.h>

#include <iostream>
#include <cstdio>
#include <string>

using namespace std;


bool hostname_to_ip(string host, string& ip);

int main(int argc,char *argv[])
{
	if(argc <2)
	{
		cout << "Please provide a hostname to resolve" << endl;
		return -1;
	}
	
	string hostname(argv[1]);
	string ip;
	bool status = hostname_to_ip(hostname , ip);
	if(!status)
	{
		cout << "failed :" << endl;
	}
	else
	{
		cout << "success:" << endl << 
			"host\t:" << hostname << endl <<
			"ip  \t:" << ip << endl;
	}
	
	return 0;	
}



bool hostname_to_ip(string hostname, string& ip)
{
	struct hostent *he;
	struct in_addr **addr_list;
	int i;
		
	if ( (he = gethostbyname( hostname.c_str() ) ) == NULL) 
		return false;

	addr_list = (struct in_addr **) he->h_addr_list;
	
	for(i = 0; addr_list[i] != NULL; i++) 
	{
		//Return the first one;
		//ip = string(inet_ntoa(*addr_list[i]));
		// AF_INET6
		// ONLY SUPPORT IPv4
		char str[INET_ADDRSTRLEN];
		ip = string(inet_ntop(AF_INET,addr_list[i],str,INET_ADDRSTRLEN));
		return true;
	}
	
	return false;
}