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 .\" *
 .\" * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
 .\" *
 .\" * This software is licensed as described in the file COPYING, which
 .\" * you should have received as part of this distribution. The terms
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 .\" *
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 .\" * copies of the Software, and permit persons to whom the Software is
 .\" * furnished to do so, under the terms of the COPYING file.
 .\" *
 .\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 .\" * KIND, either express or implied.
 .\" *
 .\" **************************************************************************
 .TH curl_multi_socket_action 3 "9 Jul 2006" "libcurl 7.16.0" "libcurl Manual"
 .SH NAME
 curl_multi_socket_action \- reads/writes available data given an action
 .SH SYNOPSIS
 .nf
 #include <curl/curl.h>

 CURLMcode curl_multi_socket_action(CURLM * multi_handle,
                                    curl_socket_t sockfd, int ev_bitmask,
                                    int *running_handles);
 .fi
 .SH DESCRIPTION
 When the application has detected action on a socket handled by libcurl, it
 should call \fIcurl_multi_socket_action(3)\fP with the \fBsockfd\fP argument
 set to the socket with the action. When the events on a socket are known, they
 can be passed as an events bitmask \fBev_bitmask\fP by first setting
 \fBev_bitmask\fP to 0, and then adding using bitwise OR (|) any combination of
 events to be chosen from CURL_CSELECT_IN, CURL_CSELECT_OUT or
 CURL_CSELECT_ERR. When the events on a socket are unknown, pass 0 instead, and
 libcurl will test the descriptor internally.

 At return, the integer \fBrunning_handles\fP points to will contain the number
 of running easy handles within the multi handle. When this number reaches
 zero, all transfers are complete/done. When you call
 \fIcurl_multi_socket_action(3)\fP on a specific socket and the counter
 decreases by one, it DOES NOT necessarily mean that this exact socket/transfer
 is the one that completed. Use \fIcurl_multi_info_read(3)\fP to figure out
 which easy handle that completed.

 The \fBcurl_multi_socket_action(3)\fP functions inform the application about
 updates in the socket (file descriptor) status by doing none, one, or multiple
 calls to the socket callback function set with the CURLMOPT_SOCKETFUNCTION
 option to \fIcurl_multi_setopt(3)\fP. They update the status with changes
 since the previous time the callback was called.

 Get the timeout time by setting the \fICURLMOPT_TIMERFUNCTION\fP option with
 \fIcurl_multi_setopt(3)\fP. Your application will then get called with
 information on how long to wait for socket actions at most before doing the
 timeout action: call the \fBcurl_multi_socket_action(3)\fP function with the
 \fBsockfd\fP argument set to CURL_SOCKET_TIMEOUT. You can also use the
 \fIcurl_multi_timeout(3)\fP function to poll the value at any given time, but
 for an event-based system using the callback is far better than relying on
 polling the timeout value.
 .SH "CALLBACK DETAILS"

 The socket \fBcallback\fP function uses a prototype like this
 .nf

   int curl_socket_callback(CURL *easy,      /* easy handle */
                            curl_socket_t s, /* socket */
                            int action,      /* see values below */
                            void *userp,    /* private callback pointer */
                            void *socketp); /* private socket pointer */

 .fi
 The callback MUST return 0.

 The \fIeasy\fP argument is a pointer to the easy handle that deals with this
 particular socket. Note that a single handle may work with several sockets
 simultaneously.

 The \fIs\fP argument is the actual socket value as you use it within your
 system.

 The \fIaction\fP argument to the callback has one of five values:
 .RS
 .IP "CURL_POLL_NONE (0)"
 register, not interested in readiness (yet)
 .IP "CURL_POLL_IN (1)"
 register, interested in read readiness
 .IP "CURL_POLL_OUT (2)"
 register, interested in write readiness
 .IP "CURL_POLL_INOUT (3)"
 register, interested in both read and write readiness
 .IP "CURL_POLL_REMOVE (4)"
 unregister
 .RE

 The \fIsocketp\fP argument is a private pointer you have previously set with
 \fIcurl_multi_assign(3)\fP to be associated with the \fIs\fP socket. If no
 pointer has been set, socketp will be NULL. This argument is of course a
 service to applications that want to keep certain data or structs that are
 strictly associated to the given socket.

 The \fIuserp\fP argument is a private pointer you have previously set with
 \fIcurl_multi_setopt(3)\fP and the CURLMOPT_SOCKETDATA option.
 .SH "RETURN VALUE"
 CURLMcode type, general libcurl multi interface error code.

 Before version 7.20.0: If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this
 basically means that you should call \fIcurl_multi_socket_action(3)\fP again
 before you wait for more actions on libcurl's sockets. You don't have to do it
 immediately, but the return code means that libcurl may have more data
 available to return or that there may be more data to send off before it is
 "satisfied".

 The return code from this function is for the whole multi stack.  Problems
 still might have occurred on individual transfers even when one of these
 functions return OK.
 .SH "TYPICAL USAGE"
 1. Create a multi handle

 2. Set the socket callback with CURLMOPT_SOCKETFUNCTION

 3. Set the timeout callback with CURLMOPT_TIMERFUNCTION, to get to know what
 timeout value to use when waiting for socket activities.

 4. Add easy handles with curl_multi_add_handle()

 5. Provide some means to manage the sockets libcurl is using, so you can check
 them for activity. This can be done through your application code, or by way
 of an external library such as libevent or glib.

 6. Call curl_multi_socket_action() to kickstart everything. To get one or more
 callbacks called.

 7. Wait for activity on any of libcurl's sockets, use the timeout value your
 callback has been told

 8, When activity is detected, call curl_multi_socket_action() for the
 socket(s) that got action. If no activity is detected and the timeout expires,
 call \fIcurl_multi_socket_action(3)\fP with \fICURL_SOCKET_TIMEOUT\fP
 .SH AVAILABILITY
 This function was added in libcurl 7.15.4, and is deemed stable since 7.16.0.
 .SH "SEE ALSO"
 .BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
 .BR curl_multi_fdset "(3), " curl_multi_info_read "(3), "
 .BR "the hiperfifo.c example"
	.\" **************************************************************************
	.\" * _ _ ____ _
	.\" * Project ___\| \| \| \| _ \\| \|
	.\" * / __\| \| \| \| \|_) \| \|
	.\" * \| (__\| \|_\| \| _ <\| \|___
	.\" * \___\|\___/\|_\| \_\_____\|
	.\" *
	.\" * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
	.\" *
	.\" * This software is licensed as described in the file COPYING, which
	.\" * you should have received as part of this distribution. The terms
	.\" * are also available at http://curl.haxx.se/docs/copyright.html.
	.\" *
	.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
	.\" * copies of the Software, and permit persons to whom the Software is
	.\" * furnished to do so, under the terms of the COPYING file.
	.\" *
	.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
	.\" * KIND, either express or implied.
	.\" *
	.\" **************************************************************************
	.TH curl_multi_socket_action 3 "9 Jul 2006" "libcurl 7.16.0" "libcurl Manual"
	.SH NAME
	curl_multi_socket_action \- reads/writes available data given an action
	.SH SYNOPSIS
	.nf
	#include <curl/curl.h>

	CURLMcode curl_multi_socket_action(CURLM * multi_handle,
	curl_socket_t sockfd, int ev_bitmask,
	int *running_handles);
	.fi
	.SH DESCRIPTION
	When the application has detected action on a socket handled by libcurl, it
	should call \fIcurl_multi_socket_action(3)\fP with the \fBsockfd\fP argument
	set to the socket with the action. When the events on a socket are known, they
	can be passed as an events bitmask \fBev_bitmask\fP by first setting
	\fBev_bitmask\fP to 0, and then adding using bitwise OR (\|) any combination of
	events to be chosen from CURL_CSELECT_IN, CURL_CSELECT_OUT or
	CURL_CSELECT_ERR. When the events on a socket are unknown, pass 0 instead, and
	libcurl will test the descriptor internally.

	At return, the integer \fBrunning_handles\fP points to will contain the number
	of running easy handles within the multi handle. When this number reaches
	zero, all transfers are complete/done. When you call
	\fIcurl_multi_socket_action(3)\fP on a specific socket and the counter
	decreases by one, it DOES NOT necessarily mean that this exact socket/transfer
	is the one that completed. Use \fIcurl_multi_info_read(3)\fP to figure out
	which easy handle that completed.

	The \fBcurl_multi_socket_action(3)\fP functions inform the application about
	updates in the socket (file descriptor) status by doing none, one, or multiple
	calls to the socket callback function set with the CURLMOPT_SOCKETFUNCTION
	option to \fIcurl_multi_setopt(3)\fP. They update the status with changes
	since the previous time the callback was called.

	Get the timeout time by setting the \fICURLMOPT_TIMERFUNCTION\fP option with
	\fIcurl_multi_setopt(3)\fP. Your application will then get called with
	information on how long to wait for socket actions at most before doing the
	timeout action: call the \fBcurl_multi_socket_action(3)\fP function with the
	\fBsockfd\fP argument set to CURL_SOCKET_TIMEOUT. You can also use the
	\fIcurl_multi_timeout(3)\fP function to poll the value at any given time, but
	for an event-based system using the callback is far better than relying on
	polling the timeout value.
	.SH "CALLBACK DETAILS"

	The socket \fBcallback\fP function uses a prototype like this
	.nf

	int curl_socket_callback(CURL easy, / easy handle */
	curl_socket_t s, /* socket */
	int action, /* see values below */
	void userp, / private callback pointer */
	void socketp); / private socket pointer */

	.fi
	The callback MUST return 0.

	The \fIeasy\fP argument is a pointer to the easy handle that deals with this
	particular socket. Note that a single handle may work with several sockets
	simultaneously.

	The \fIs\fP argument is the actual socket value as you use it within your
	system.

	The \fIaction\fP argument to the callback has one of five values:
	.RS
	.IP "CURL_POLL_NONE (0)"
	register, not interested in readiness (yet)
	.IP "CURL_POLL_IN (1)"
	register, interested in read readiness
	.IP "CURL_POLL_OUT (2)"
	register, interested in write readiness
	.IP "CURL_POLL_INOUT (3)"
	register, interested in both read and write readiness
	.IP "CURL_POLL_REMOVE (4)"
	unregister
	.RE

	The \fIsocketp\fP argument is a private pointer you have previously set with
	\fIcurl_multi_assign(3)\fP to be associated with the \fIs\fP socket. If no
	pointer has been set, socketp will be NULL. This argument is of course a
	service to applications that want to keep certain data or structs that are
	strictly associated to the given socket.

	The \fIuserp\fP argument is a private pointer you have previously set with
	\fIcurl_multi_setopt(3)\fP and the CURLMOPT_SOCKETDATA option.
	.SH "RETURN VALUE"
	CURLMcode type, general libcurl multi interface error code.

	Before version 7.20.0: If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this
	basically means that you should call \fIcurl_multi_socket_action(3)\fP again
	before you wait for more actions on libcurl's sockets. You don't have to do it
	immediately, but the return code means that libcurl may have more data
	available to return or that there may be more data to send off before it is
	"satisfied".

	The return code from this function is for the whole multi stack. Problems
	still might have occurred on individual transfers even when one of these
	functions return OK.
	.SH "TYPICAL USAGE"
	1. Create a multi handle

	2. Set the socket callback with CURLMOPT_SOCKETFUNCTION

	3. Set the timeout callback with CURLMOPT_TIMERFUNCTION, to get to know what
	timeout value to use when waiting for socket activities.

	4. Add easy handles with curl_multi_add_handle()

	5. Provide some means to manage the sockets libcurl is using, so you can check
	them for activity. This can be done through your application code, or by way
	of an external library such as libevent or glib.

	6. Call curl_multi_socket_action() to kickstart everything. To get one or more
	callbacks called.

	7. Wait for activity on any of libcurl's sockets, use the timeout value your
	callback has been told

	8, When activity is detected, call curl_multi_socket_action() for the
	socket(s) that got action. If no activity is detected and the timeout expires,
	call \fIcurl_multi_socket_action(3)\fP with \fICURL_SOCKET_TIMEOUT\fP
	.SH AVAILABILITY
	This function was added in libcurl 7.15.4, and is deemed stable since 7.16.0.
	.SH "SEE ALSO"
	.BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
	.BR curl_multi_fdset "(3), " curl_multi_info_read "(3), "
	.BR "the hiperfifo.c example"