Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

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)

Check Out this Related Man Page

ARES_QUERY(3)						     Library Functions Manual						     ARES_QUERY(3)

NAME
ares_query - Initiate a single-question DNS query SYNOPSIS
#include <ares.h> typedef void (*ares_callback)(void *arg, int status, int timeouts, unsigned char *abuf, int alen) void ares_query(ares_channel channel, const char *name, int dnsclass, int type, ares_callback callback, void *arg) DESCRIPTION
The ares_query function initiates a single-question DNS query on the name service channel identified by channel. The parameter name gives the query name as a NUL-terminated C string of period-separated labels optionally ending with a period; periods and backslashes within a label must be escaped with a backslash. The parameters dnsclass and type give the class and type of the query using the values defined in <arpa/nameser.h>. 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_query 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 successfully. ARES_ENODATA The query completed but contains no answers. ARES_EFORMERR The query completed but the server claims that the query was malformatted. ARES_ESERVFAIL The query completed but the server claims to have experienced a failure. (This code can only occur if the ARES_FLAG_NOCHECKRESP flag was specified at channel initialization time; otherwise, such responses are ignored at the ares_send(3) level.) ARES_ENOTFOUND The query completed but the queried-for domain name was not found. ARES_ENOTIMP The query completed but the server does not implement the operation requested by the query. (This code can only occur if the ARES_FLAG_NOCHECKRESP flag was specified at channel initialization time; otherwise, such responses are ignored at the ares_send(3) level.) ARES_EREFUSED The query completed but the server refused the query. (This code can only occur if the ARES_FLAG_NOCHECKRESP flag was specified at channel initialization time; otherwise, such responses are ignored at the ares_send(3) level.) ARES_EBADNAME The query name name could not be encoded as a domain name, either because it contained a zero-length label or because it contained a label of more than 63 characters. 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 (even if there was something wrong with it, as indicated by some of the above error codes), 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. SEE ALSO
ares_process(3) AUTHOR
Greg Hudson, MIT Information Systems Copyright 1998 by the Massachusetts Institute of Technology. 24 July 1998 ARES_QUERY(3)
Man Page