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curl_multi_socket_action(3)	libcurl	Manual	   curl_multi_socket_action(3)

       curl_multi_socket_action	- reads/writes available data given an action

       #include	<curl/curl.h>

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

       When  the  application  has  detected  action  on  a  socket handled by
       libcurl,	it should call curl_multi_socket_action(3) with	the sockfd ar-
       gument  set  to the socket with the action. When	the events on a	socket
       are known, they can be passed as	an events bitmask ev_bitmask by	 first
       setting	ev_bitmask to 0, and then adding using bitwise OR (|) any com-
       bination	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.  It  is  also
       permissible  to pass CURL_SOCKET_TIMEOUT	to the sockfd parameter	in or-
       der to initiate the whole process or when a timeout occurs.

       At return, running_handles points to the	number of running easy handles
       within  the  multi handle. When this number reaches zero, all transfers
       are complete/done. When you call	curl_multi_socket_action(3) on a  spe-
       cific  socket and the counter decreases by one, it DOES NOT necessarily
       mean that this exact socket/transfer is the  one	 that  completed.  Use
       curl_multi_info_read(3) to figure out which easy	handle that completed.

       The  curl_multi_socket_action(3)	function informs 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 CURL-
       MOPT_SOCKETFUNCTION(3) option to	curl_multi_setopt(3). They update  the
       status with changes since the previous time the callback	was called.

       Get  the	 timeout  time by setting the CURLMOPT_TIMERFUNCTION(3)	option
       with curl_multi_setopt(3). 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 curl_multi_socket_action(3)	function  with
       the  sockfd  argument  set to CURL_SOCKET_TIMEOUT. You can also use the
       curl_multi_timeout(3) 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.

       1. Create a multi handle

       2. Set the socket callback with CURLMOPT_SOCKETFUNCTION(3)

       3. Set the timeout callback with	CURLMOPT_TIMERFUNCTION(3), 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(..., CURL_SOCKET_TIMEOUT, 0, ...)  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 curl_multi_socket_action(3) with CURL_SOCKET_TIMEOUT.

       This  function  was added in libcurl 7.15.4, and	is deemed stable since

       curl_multi_cleanup(3),	  curl_multi_init(3),	  curl_multi_fdset(3),
       curl_multi_info_read(3),	the hiperfifo.c	example

libcurl	7.72.0			 June 10, 2019	   curl_multi_socket_action(3)


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