Display the IP addresses of a host using C++ and UNIX sockets

showip.cpp

#include <iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <cstdlib>
#include <string>

using namespace std;

int main() {
    addrinfo serverinfo, *result, *ptr;
    int ret = 0;

    memset(&hints,0,sizeof(serverinfo));
    serverinfo.ai_family = AF_UNSPEC; // fill this struct partially
    serverinfo.ai_socktype = SOCK_STREAM;

    string input = "";
    cout << "Whats the host's name: ";
    getline(cin,input);

    if((ret = getaddrinfo(input.c_str(),NULL,&serverinfo,&result)) != 0){
        cerr << "getaddrinfo(): "<<input <<"-" << gai_strerror(ret) << "\n";
        return 0;
    }

    cout << "IP addresses for "<< input << endl;

    // Loop through all the linked list of address and get the ip addresses
    for(ptr = result; ptr != NULL; ptr = ptr->ai_next){
        void *addr;
        string ipver;

        if(p->ai_family == AF_INET){
            // IPv4 address
            sockaddr_in *ipv4 = (sockaddr_in*)p->ai_addr;
            addr = &(ipv4->sin_addr);
            ipver = "IPv4";
        }
        else{
            // IPv6 address
            sockaddr_in6 *ipv6 = (sockaddr_in6*)p->ai_addr;
            addr = &(ipv6->sin6_addr);
            ipver = "IPv6";
        }

        // use INET6_ADDRSTRLEN becuase we need it to big enough
        // convert the ip from network(bits) to presentation(eg. 127.0.0.1)
        char ipAddress[INET6_ADDRSTRLEN];
        inet_ntop(p->ai_family, addr, ipstr, sizeof(ipAddress));
        // print it out
        cout << ipver <<" " << ipstr << endl;
    }

    // free the memory
    freeaddrinfo(res);
    return 0;
}