getting ip address : gethostbyname()

[fnoyan]

Hi

Why do we use a sockaddr_in structure in order to get the ip address of any host whose ip information is retrieved with gethostbyname() and why can't we use h_addr_list elements directly!

For exmaple

// whis works
struct hostent *h;
struct sockaddr_in sa;
h = gethostbyname(hostname);

for (i=0; h->h_addr_list[i]; i++) {
      memcpy ( &sa.sin_addr.s_addr, he.h_addr_list[nAdapter],he.h_length);
      printf("Address: %s\n", inet_ntoa(sa.sin_addr)); 
   }

// this fails!
struct hostent *h;
h = gethostbyname(hostname);

for (i=0; h->h_addr_list[i]; i++) {
      printf("Address: %s\n", h->h_addr_list[i]); 
   }

the array elements in h_addr_list are *char. So, whay cannot we directly use those value?

[SKeane]

h_addr_list is a pointer to an array of pointers to addresses. Before IPv6 came along, the array was an array of pointers to in_addr structures. After IPv6 (if implemented) it is an array of pointers to either in_addr or in6_addr structures. It's unfortunate that they are defined as "char *" pointers as that causes confusion. They are not strings, which is why your program fails.