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ares_process(3) [centos man page]

ARES_PROCESS(3) 					     Library Functions Manual						   ARES_PROCESS(3)

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)

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ARES_SEND(3)						     Library Functions Manual						      ARES_SEND(3)

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)
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