NAME

       curl_multi_socket - reads/writes available data

SYNOPSIS

       #include <curl/curl.h>
       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);

DESCRIPTION

       These functions are deprecated. Do not use! See curl_multi_socket_action(3) instead!

       At  return, the integer running_handles 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 curl_multi_socket_action(3) 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 curl_multi_info_read(3) to figure out which
       easy handle that completed.

       The curl_multi_socket_action(3) 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  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   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.

       Usage  of  curl_multi_socket(3)  is  deprecated,  whereas  the  function  is equivalent to
       curl_multi_socket_action(3) with ev_bitmask set to 0.

       Force libcurl to (re-)check all its internal sockets  and  transfers  instead  of  just  a
       single  one  by calling curl_multi_socket_all(3). Note that there should not be any reason
       to use this function!

CALLBACK DETAILS

       The socket callback function uses a prototype like this

         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 */

       The callback MUST return 0.

       The easy 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 s argument is the actual socket value as you use it within your system.

       The action argument to the callback has one of five values:

              CURL_POLL_NONE (0)
                     register, not interested in readiness (yet)

              CURL_POLL_IN (1)
                     register, interested in read readiness

              CURL_POLL_OUT (2)
                     register, interested in write readiness

              CURL_POLL_INOUT (3)
                     register, interested in both read and write readiness

              CURL_POLL_REMOVE (4)
                     unregister

       The   socketp   argument   is   a   private   pointer   you   have   previously  set  with
       curl_multi_assign(3) to be associated with the s 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 userp argument is a private pointer you have previously set with  curl_multi_setopt(3)
       and the CURLMOPT_SOCKETDATA option.

RETURN VALUE

       CURLMcode type, general libcurl multi interface error code.

       Legacy: If you receive CURLM_CALL_MULTI_PERFORM, this basically means that you should call
       curl_multi_socket(3) 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".

       In modern libcurls, CURLM_CALL_MULTI_PERFORM  or  CURLM_CALL_MULTI_SOKCET  should  not  be
       returned and no application needs to care about them.

       NOTE that the return code is for the whole multi stack. Problems still might have occurred
       on individual transfers even when one of these functions return OK.

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
       curl_multi_socket_action(3) with CURL_SOCKET_TIMEOUT

       8. Go back to step 6.

AVAILABILITY

       This function was added in libcurl 7.15.4, and is deemed stable since 7.16.0.

       curl_multi_socket(3) is deprecated, use curl_multi_socket_action(3) instead!

SEE ALSO

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