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_t *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_ENODATA       There was no data returned to extract a result from.

       ARES_ENOTFOUND     The name name 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.

       When the associated callback is called, it is called with a channel lock so care must be taken to  ensure
       any processing is minimal to prevent DNS channel stalls.

       The callback may be triggered from a different thread than the one which called ares_gethostbyname(3).

       For integrators running their own event loops and not using ARES_OPT_EVENT_THREAD, care needs to be taken
       to ensure any file descriptor lists are updated immediately within the eventloop when notified.

SEE ALSO

       ares_process(3), ares_gethostbyaddr(3)

                                                  25 July 1998                             ARES_GETHOSTBYNAME(3)