ares_gethostbyname - Initiate a host query by name
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)
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
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)
The callback argument arg
is copied from the ares_gethostbyname
. The callback argument status
indicates whether the
query succeeded and, if not, how it failed. It may have any of the following
- The host lookup completed successfully.
- The ares library does not know how to find addresses of
- The hostname name is composed entirely of numbers
and periods, but is not a valid representation of an Internet
- The address addr was not found.
- Memory was exhausted.
- The query was cancelled.
- 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
Greg Hudson, MIT Information Systems
Copyright 1998 by the Massachusetts Institute of Technology.