ares_process(3) [debian man page]

ARES_PROCESS(3) 					     Library Functions Manual						   ARES_PROCESS(3)

NAME

       ares_process - Process events for name resolution

SYNOPSIS

       #include <ares.h>

       void ares_process(ares_channel channel, fd_set *read_fds,
       fd_set *write_fds)

       void ares_process_fd(ares_channel channel, ares_socket_t read_fd, ares_socket_t write_fd)

DESCRIPTION

       The  ares_process(3)  function handles input/output events and timeouts associated with queries pending on the name service channel identi-
       fied by channel.  The file descriptor sets pointed to by read_fds and write_fds should have file  descriptors  set  in  them  according	to
       whether the file descriptors specified by ares_fds(3) are ready for reading and writing.  (The easiest way to determine this information is
       to invoke select with a timeout no greater than the timeout given by ares_timeout(3) ).

       The ares_process function will invoke callbacks for pending queries if they complete successfully or fail.

       ares_process_fd(3) works the same way but acts and operates only on the specific file descriptors (sockets) you pass in	to  the  function.
       Use  ARES_SOCKET_BAD  for  "no action". This function is of course provided to allow users of c-ares to void select() in their applications
       and within c-ares.

   EXAMPLE
       The following code fragment waits for all pending queries on a channel to complete:

	      int nfds, count;
	      fd_set readers, writers;
	      struct timeval tv, *tvp;

	      while (1)
		{
		  FD_ZERO(&readers);
		  FD_ZERO(&writers);
		  nfds = ares_fds(channel, &readers, &writers);
		  if (nfds == 0)
		    break;
		  tvp = ares_timeout(channel, NULL, &tv);
		  count = select(nfds, &readers, &writers, NULL, tvp);
		  ares_process(channel, &readers, &writers);
		}

SEE ALSO

       ares_fds(3), ares_timeout(3)

AUTHOR

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

								   25 July 1998 						   ARES_PROCESS(3)

ARES_SEND(3)						     Library Functions Manual						      ARES_SEND(3)

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_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)