gethostbyaddr()

Description

Get host information corresponding to an address.

#include <winsock.h>

struct hostent FAR * PASCAL FAR gethostbyaddr ( const char FAR * addr, int len, int type );

addr

A pointer to an address in network byte order.
len
The length of the address, which must be 4 for PF_INET addresses.
type
The type of the address, which must be PF_INET.

Remarks

gethostbyaddr() returns a pointer to the following structure which contains the name(s) and address which correspond to the given address.

struct hostent {        char FAR *      h_name;
        char FAR * FAR *h_aliases;
        short           h_addrtype;
        short           h_length;
        char FAR * FAR *h_addr_list;
};

The members of this structure are:

h_name

Official name of the host (PC).
h_aliases
A NULL -terminated array of alternate names.
h_addrtype
The type of address being returned; for Windows Sockets this is always PF_INET.
h_length
The length, in bytes, of each address; for PF_INET, this is always 4.
h_addr_list
A NULL-terminated list of addresses for the host. Addresses are returned in network byte order.

The macro h_addr is defined to be h_addr_listφ0∙ for compatibility with older software.

The pointer which is returned points to a structure which is allocated by the Windows Sockets implementation. The application must never attempt to modify this structure or to free any of its components. Furthermore, only one copy of this structure is allocated per thread, and so the application should copy any information which it needs before issuing any other Windows Sockets API calls.

Return Value

If no error occurs, gethostbyaddr() returns a pointer to the hostent structure described above. Otherwise it returns a NULL pointer and a specific error number may be retrieved by calling WSAGetLastError()

Error Codes

WSANOTINITIALISED

A successful WSAStartup() must occur before using this API.
WSAENETDOWN
The Windows Sockets implementation has detected that the network subsystem has failed.
WSAHOST_NOT_FOUND
Authoritative Answer Host not found.
WSATRY_AGAIN
Non-Authoritative Host not found, or SERVERFAIL.
WSANO_RECOVERY
Non recoverable errors, FORMERR, REFUSED, NOTIMP.
WSANO_DATA
Valid name, no data record of requested type.
WSAEINPROGRESS
A blocking Windows Sockets operation is in progress.
WSAEINTR
The (blocking) call was canceled via WSACancelBlockingCall()

See Also

WSAAsyncGetHostByAddr(), gethostbyname(),

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