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docs/ares_getsock.3
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David Hotham
const is fine on ares__channel_[un]lock (#758)
22 май 2024, 14:40
22 май 2024, 14:402f200b9
.\"
.\" Copyright 1998 by Daniel Stenberg
.\" SPDX-License-Identifier: MIT
.\"
.TH ARES_GETSOCK 3 "11 March 2010"
.SH NAME
ares_getsock \- get socket descriptors to wait on (deprecated)
.SH SYNOPSIS
.nf
#include <ares.h>

int ares_getsock(const ares_channel_t *\fIchannel\fP, ares_socket_t *\fIsocks\fP,
                 int \fInumsocks\fP);
.fi
.SH DESCRIPTION
The
.B ares_getsock
function retrieves the set of socket descriptors which the calling
application should wait on for reading and/or writing for the
processing of name service queries pending on the name service channel
identified by
.IR channel .
Socket descriptors will be set in the socket descriptor array pointed to by
\fIsocks\fP.
\fInumsocks\fP is the size of the given array in number of ints.

This function can only return information up to 16 sockets. If more are
in use, they are simply not reported back.
.SH RETURN VALUES
\fBares_getsock\fP returns a bitmask for what actions to wait for on the
different sockets. The ares.h header file provides these convenience macros to
extract the information appropriately:

.nf
#define ARES_GETSOCK_MAXNUM 16 /* ares_getsock() can return info about
                                  this many sockets */
#define ARES_GETSOCK_READABLE(bits,num) (bits & (1<< (num)))
#define ARES_GETSOCK_WRITABLE(bits,num) (bits & (1 << ((num) + \
                                         ARES_GETSOCK_MAXNUM)))
.fi
.SH NOTES
This function was added in c-ares 1.3.1 and deprecated in c-ares 1.20.0 due to
the implementation of \fBARES_OPT_MAX_UDP_QUERIES\fP which makes it likely to
exceed 16 open file descriptors.

It is recommended to use \fBARES_OPT_EVENT_THREAD\fP passed to
\fIares_init_options(3)\fP or to use socket state callbacks
(\fBARES_OPT_SOCK_STATE_CB\fP) registered via \fBares_init_options(3)\fP.
.SH SEE ALSO
.BR ares_init_options (3),
.BR ares_timeout (3),
.BR ares_fds (3),
.BR ares_process (3)