IPC Socket - using gethostbyaddr(3) Function

The gethostbyaddr(3) Function

There are times where you have an Internet address, but you need to report the hostname instead of the IP number. A server might want to log the hostname of the client that has contacted it, instead of the IP number alone. The function synopsis for gethostbyaddr(3) is as follows:

#include <sys/socket.h> /* for AF_INET */

struct hostent *gethostbyaddr(

const char *addr, /* Input address */

int len,          /* Address length */

int type);        /* Address type */

The gethostbyaddr(3) function accepts three input arguments. They

are

1. The input address (addr) to be converted into a hostname. For address type AF_INET, this is the pointer to the sin_addr member of the address structure.
2. The length of the input address (len). For type AF_INET, this will be the value 4 (4 bytes). For type AF_INET6, this value will be 16.
3. The type of the input address (type), which is the value AF_INET or AF_INET6.

Notice that the first argument is a character pointer, allowing it to potentially accept many forms of addresses. You will need to cast your address pointer to (char *) to satisfy the compiler. The second argument indicates the length of the supplied address.

The third argument is the type of the address being passed. It is AF_INET for an IPv4 Internet address, or in the future, it will be the value AF_INET6 for an IPv6 format address.

Example:

Sample C code using gethostbyaddr function