11.4 gethostbyaddr
Function
The function gethostbyaddr takes a
binary IPv4 address and tries to find the hostname corresponding to
that address. This is the reverse of gethostbyname.
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#include <netdb.h>
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struct hostent *gethostbyaddr (const char
*addr, socklen_t
len, int family);
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Returns: non-null pointer if OK, NULL
on error with h_errno set
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This function returns a pointer to the same
hostent structure that we described with
gethostbyname. The field of interest in this structure is
normally h_name, the canonical hostname.
The addr
argument is not a char*, but is really a pointer to an
in_addr structure containing the IPv4 address.
len is the size of this structure:
4 for an IPv4 address. The family
argument is AF_INET.
In terms of the DNS, gethostbyaddr
queries a name server for a PTR record in the in-addr.arpa
domain.
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