docs/libcurl/curl_multi_socket.3 - third_party/curl - Git at Google

 .\" $Id$
 .\"
 .TH curl_multi_socket 3 "9 Jul 2006" "libcurl 7.16.0" "libcurl Manual"
 .SH NAME
 curl_multi_socket \- reads/writes available data
 .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);

 CURLMcode curl_multi_socket(CURLM * multi_handle, curl_socket_t sockfd,
                             int *running_handles);

 CURLMcode curl_multi_socket_all(CURLM *multi_handle,
                                 int *running_handles);
 .fi
 .SH DESCRIPTION
 Alternative versions of \fIcurl_multi_perform(3)\fP that allows the
 application to pass in the file descriptor/socket that has been detected to
 have \&"action" on it and let libcurl perform. This allows libcurl to not have
 to scan through all possible file descriptors to check for action. 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 int \fBrunning_handles\fP points to will contain the number of
 still running easy handles within the multi handle. When this number reaches
 zero, all transfers are complete/done. Note that 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 curl_multi_socket 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 this function was called.

 Force libcurl to (re-)check all its internal sockets and transfers instead of
 just a single one by calling \fBcurl_multi_socket_all(3)\fP. Note that there
 should rarely be reasons to use this function!

 Get the timeout time - how long to wait for socket actions at most before
 doing the timeout action: call the \fBcurl_multi_socket(3)\fP function with
 the \fBsockfd\fP argument set to CURL_SOCKET_TIMEOUT, by setting the
 \fICURLMOPT_TIMERFUNCTION\fP option with \fIcurl_multi_setopt(3)\fP. 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.

 Usage of \fIcurl_multi_socket(3)\fP is deprecated, whereas the function is
 equivalent to \fIcurl_multi_socket_action(3)\fP, when \fBev_bitmask\fP is set
 to 0.

 .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.

 If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this basically means that you
 should call \fIcurl_multi_socket(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".

 NOTE that this only returns errors etc regarding the whole multi stack. There
 might still have occurred problems on individual transfers even when this
 function returns 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. Wait for activity on any of libcurl's sockets, use the timeout value your
 callback has been told

 7, 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

 8. Go back to step 6.
 .SH AVAILABILITY
 This function was added in libcurl 7.15.4, although deemed stable since
 7.16.0.

 \fIcurl_multi_socket(3)\fP is deprecated, use
 \fIcurl_multi_socket_action(3)\fP instead!
 .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"
	.\" $Id$
	.\"
	.TH curl_multi_socket 3 "9 Jul 2006" "libcurl 7.16.0" "libcurl Manual"
	.SH NAME
	curl_multi_socket \- reads/writes available data
	.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);

	CURLMcode curl_multi_socket(CURLM * multi_handle, curl_socket_t sockfd,
	int *running_handles);

	CURLMcode curl_multi_socket_all(CURLM *multi_handle,
	int *running_handles);
	.fi
	.SH DESCRIPTION
	Alternative versions of \fIcurl_multi_perform(3)\fP that allows the
	application to pass in the file descriptor/socket that has been detected to
	have \&"action" on it and let libcurl perform. This allows libcurl to not have
	to scan through all possible file descriptors to check for action. 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 int \fBrunning_handles\fP points to will contain the number of
	still running easy handles within the multi handle. When this number reaches
	zero, all transfers are complete/done. Note that 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 curl_multi_socket 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 this function was called.

	Force libcurl to (re-)check all its internal sockets and transfers instead of
	just a single one by calling \fBcurl_multi_socket_all(3)\fP. Note that there
	should rarely be reasons to use this function!

	Get the timeout time - how long to wait for socket actions at most before
	doing the timeout action: call the \fBcurl_multi_socket(3)\fP function with
	the \fBsockfd\fP argument set to CURL_SOCKET_TIMEOUT, by setting the
	\fICURLMOPT_TIMERFUNCTION\fP option with \fIcurl_multi_setopt(3)\fP. 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.

	Usage of \fIcurl_multi_socket(3)\fP is deprecated, whereas the function is
	equivalent to \fIcurl_multi_socket_action(3)\fP, when \fBev_bitmask\fP is set
	to 0.

	.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.

	If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this basically means that you
	should call \fIcurl_multi_socket(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".

	NOTE that this only returns errors etc regarding the whole multi stack. There
	might still have occurred problems on individual transfers even when this
	function returns 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. Wait for activity on any of libcurl's sockets, use the timeout value your
	callback has been told

	7, 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

	8. Go back to step 6.
	.SH AVAILABILITY
	This function was added in libcurl 7.15.4, although deemed stable since
	7.16.0.

	\fIcurl_multi_socket(3)\fP is deprecated, use
	\fIcurl_multi_socket_action(3)\fP instead!
	.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"