NAME¶
ares_gethostbyname - Initiate a host query by name
SYNOPSIS¶
#include <ares.h>
typedef void (*ares_host_callback)(void *arg, int status,
int timeouts, struct hostent *hostent)
void ares_gethostbyname(ares_channel channel, const char *name,
int family, ares_host_callback callback, void *arg)
DESCRIPTION¶
The
ares_gethostbyname function initiates a host query by name on the
name service channel identified by
channel. The parameter
name
gives the hostname as a NUL-terminated C string, and
family gives the
desired type of address for the resulting host entry. When the query is
complete or has failed, the ares library will invoke
callback.
Completion or failure of the query may happen immediately, or may happen
during a later call to
ares_process(3),
ares_destroy(3) or
ares_cancel(3).
The callback argument
arg is copied from the
ares_gethostbyname
argument
arg. The callback argument
status indicates whether the
query succeeded and, if not, how it failed. It may have any of the following
values:
- ARES_SUCCESS
- The host lookup completed successfully.
- ARES_ENOTIMP
- The ares library does not know how to find addresses of type
family.
- ARES_EBADNAME
- The hostname name is composed entirely of numbers and periods, but
is not a valid representation of an Internet address.
- ARES_ENOTFOUND
- The address addr was not found.
- ARES_ENOMEM
- Memory was exhausted.
- ARES_ECANCELLED
- The query was cancelled.
- ARES_EDESTRUCTION
- The name service channel channel is being destroyed; the query will
not be completed.
The callback argument
timeouts reports how many times a query timed out
during the execution of the given request.
On successful completion of the query, the callback argument
hostent
points to a
struct hostent containing the name of the host returned by
the query. The callback need not and should not attempt to free the memory
pointed to by
hostent; the ares library will free it when the callback
returns. If the query did not complete successfully,
hostent will be
NULL.
SEE ALSO¶
ares_process(3),
ares_gethostbyaddr(3)
AUTHOR¶
Greg Hudson, MIT Information Systems
Copyright 1998 by the Massachusetts Institute of Technology.