Gethostbyaddr ()

Brief description of gethostbyaddr:

Returns the host information corresponding to the given address.

# Include <Winsock. h>

Struct hostent far * Pascal far gethostbyaddr (const char

Far * ADDR, int Len, int type );

ADDR: pointer to the byte sequential address of the network.

Len: the length of the address. The value is 4 in the pf_inet type.

Type: Address type, which must be pf_inet.

Note:

Gethostbyaddr () returns the hostent structure pointer corresponding to the given address that contains the Host Name and address information. The structure declaration is as follows:

Struct hostent {

Char far * h_name;

Char far * h_aliases;

Short h_addrtype;

Short h_length;

Char far * h_addr_list;

};

Structure members include:

Member Purpose

H_name: Specifies the Host Name (PC ).

H_aliases: an optional host name queue ending with a null pointer.

H_addrtype: Type of the returned address. For Windows Sockets, this field is always pf_inet.

H_legnth the length (number of bytes) of each address, which corresponds to 4 in the pf_inet domain.

H_addr_list should be a list of host addresses ending with a null pointer, and the returned addresses are in network order

To ensure the compatibility of other old software, h_addr_list [0] is defined as macro h_addr.

The returned Pointer Points to a structure allocated by Windows Sockets. The application should not try to modify this structure or release any part of it. In addition, each thread only has a copy of this structure, so the application should copy the information it needs before calling other Windows scokets APIs.

Return Value:

If no error occurs, gethostbyaddr () returns a pointer to the hostent structure described above. Otherwise, a null pointer is returned. The application can get a specific error code through wsagetlasterror.

Error code:

Wsanotintialised must successfully call wsastartup () before applying this API ().

Wsaentdown Windows Sockets implementation detected network subsystem errors.

Wsahost_not_found does not find the authorization response host.

Wsatry_again does not find an unauthorized host or serverfail.

Errors that cannot be recovered by wsano_retimp, such as formerr, refused, and noibd.

Wsano_data is a valid name, but there is no data record about the request type.

Wsaeinprogress a blocked Windows Sockets operation is in progress.

Wsacancelblockingcall () canceled the blocked wsaeintr call.