NAME

       ares_send - Initiate a DNS query

SYNOPSIS

       #include <ares.h>

       typedef void (*ares_callback)(void *arg, int status,
       int timeouts, unsigned char *abuf, int alen)

       void ares_send(ares_channel channel, const unsigned char *qbuf,
            int qlen, ares_callback callback, void *arg)

DESCRIPTION

       The  ares_send  function  initiates  a  DNS query on the name service channel identified by channel.  The
       parameters qbuf and qlen give the DNS query, which should already have been formatted  according  to  the
       DNS  protocol.   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) or ares_destroy(3).

       The  callback  argument  arg  is  copied  from  the ares_send 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 query completed.

       ARES_EBADQUERY     The  query  buffer  was poorly formed (was not long enough for a DNS header or was too
                          long for TCP transmission).

       ARES_ETIMEOUT      No name servers responded within the timeout period.

       ARES_ECONNREFUSED  No name servers could be contacted.

       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.

       If  the  query  completed,  the  callback argument abuf points to a result buffer of length alen.  If the
       query did not complete, abuf will be NULL and alen will be 0.

       Unless the flag ARES_FLAG_NOCHECKRESP was set at channel initialization  time,  ares_send  will  normally
       ignore  responses  whose  questions  do  not match the questions in qbuf, as well as responses with reply
       codes of SERVFAIL, NOTIMP, and REFUSED.  Unlike other query  functions  in  the  ares  library,  however,
       ares_send  does  not  inspect the header of the reply packet to determine the error status, so a callback
       status of ARES_SUCCESS does not reflect as much about the response as for other query functions.

SEE ALSO

       ares_process(3)

AUTHOR

       Greg Hudson, MIT Information Systems
       Copyright 1998 by the Massachusetts Institute of Technology.

                                                  25 July 1998                                      ARES_SEND(3)