sample program for getaddrinfo and inet_atop

resolve_hostname.c

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>

typedef struct sockaddr_in SA4;
typedef struct sockaddr_in6 SA6;

int main(int argc, char **argv){
    char *hostname = argv[1];
    char *service = argv[2];
    struct addrinfo hints, *res0, *res;
    int err;
    int sock;
    char paddr[128];

    memset(&hints, 0, sizeof(hints));
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_family = AF_UNSPEC;

    if ((err = getaddrinfo(hostname, service, &hints, &res0)) != 0) {
        printf("error %d\n", err);
        return 1;
    }

    if (res0 == NULL) {
        printf("failed\n");
        return 1;
    }

    for (res=res0; res!=NULL; res=res->ai_next) {
        if(res->ai_family == AF_INET ){
            SA4 *socaddr_v4 = (SA4 *)res->ai_addr;
            inet_ntop(res->ai_family, &(socaddr_v4->sin_addr), paddr, 128);
            printf("%s %d\n", paddr, ntohs(socaddr_v4->sin_port));
        }
        if(res->ai_family == AF_INET6 ){
            SA6 *socaddr_v6 = (SA6 *)res->ai_addr;
            inet_ntop(res->ai_family, &(socaddr_v6->sin6_addr), paddr, 128);
            printf("%s %d\n", paddr, ntohs(socaddr_v6->sin6_port));
        }
    }

    freeaddrinfo(res0);

    return 0;
}