1curl_multi_socket(3)            libcurl Manual            curl_multi_socket(3)
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NAME

6       curl_multi_socket - reads/writes available data
7

SYNOPSIS

9       #include <curl/curl.h>
10       CURLMcode curl_multi_socket(CURLM * multi_handle, curl_socket_t sockfd,
11                                   int *running_handles);
12
13       CURLMcode curl_multi_socket_all(CURLM *multi_handle,
14                                       int *running_handles);
15

DESCRIPTION

17       These     functions     are     deprecated.    Do    not    use!    See
18       curl_multi_socket_action(3) instead!
19
20       At return, the integer running_handles points to will contain the  num‐
21       ber  of  still  running easy handles within the multi handle. When this
22       number reaches zero, all transfers are complete/done.  Note  that  when
23       you  call  curl_multi_socket_action(3)  on  a  specific  socket and the
24       counter decreases by one, it DOES NOT necessarily mean that this  exact
25       socket/transfer  is the one that completed. Use curl_multi_info_read(3)
26       to figure out which easy handle that completed.
27
28       The curl_multi_socket_action(3) functions inform the application  about
29       updates  in  the socket (file descriptor) status by doing none, one, or
30       multiple calls to the socket  callback  function  set  with  the  CURL‐
31       MOPT_SOCKETFUNCTION(3)  option to curl_multi_setopt(3). They update the
32       status with changes since the previous time the callback was called.
33
34       Get the timeout time by setting  the  CURLMOPT_TIMERFUNCTION(3)  option
35       with  curl_multi_setopt(3).  Your application will then get called with
36       information on how long to wait for socket actions at most before doing
37       the  timeout action: call the curl_multi_socket_action(3) function with
38       the sockfd argument set to CURL_SOCKET_TIMEOUT. You can  also  use  the
39       curl_multi_timeout(3) function to poll the value at any given time, but
40       for an event-based system using the callback is far better than relying
41       on polling the timeout value.
42
43       Usage  of  curl_multi_socket(3)  is deprecated, whereas the function is
44       equivalent to curl_multi_socket_action(3) with ev_bitmask set to 0.
45
46       Force libcurl to (re-)check all  its  internal  sockets  and  transfers
47       instead  of just a single one by calling curl_multi_socket_all(3). Note
48       that there should not be any reason to use this function!
49

CALLBACK DETAILS

51       The socket callback function uses a prototype like this
52
53         int curl_socket_callback(CURL *easy,      /* easy handle */
54                                  curl_socket_t s, /* socket */
55                                  int action,      /* see values below */
56                                  void *userp,    /* private callback pointer */
57                                  void *socketp); /* private socket pointer */
58
59       The callback MUST return 0.
60
61       The easy argument is a pointer to the easy handle that deals with  this
62       particular  socket.  Note  that  a  single handle may work with several
63       sockets simultaneously.
64
65       The s argument is the actual socket value as you  use  it  within  your
66       system.
67
68       The action argument to the callback has one of five values:
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70              CURL_POLL_NONE (0)
71                     register, not interested in readiness (yet)
72
73              CURL_POLL_IN (1)
74                     register, interested in read readiness
75
76              CURL_POLL_OUT (2)
77                     register, interested in write readiness
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79              CURL_POLL_INOUT (3)
80                     register, interested in both read and write readiness
81
82              CURL_POLL_REMOVE (4)
83                     unregister
84
85       The  socketp argument is a private pointer you have previously set with
86       curl_multi_assign(3) to be associated with the s socket. If no  pointer
87       has  been  set, socketp will be NULL. This argument is of course a ser‐
88       vice to applications that want to keep certain data or structs that are
89       strictly associated to the given socket.
90
91       The  userp  argument  is a private pointer you have previously set with
92       curl_multi_setopt(3) and the CURLMOPT_SOCKETDATA(3) option.
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RETURN VALUE

95       CURLMcode type, general libcurl multi interface error code.
96
97       Legacy: If you receive CURLM_CALL_MULTI_PERFORM, this  basically  means
98       that  you  should  call curl_multi_socket(3) again, before you wait for
99       more actions on libcurl's sockets. You don't have to do it immediately,
100       but  the return code means that libcurl may have more data available to
101       return or that there may be more data to send off before it is  "satis‐
102       fied".
103
104       In modern libcurls, CURLM_CALL_MULTI_PERFORM or CURLM_CALL_MULTI_SOCKET
105       should not be returned and no application needs to care about them.
106
107       NOTE that the return code is for the whole multi stack. Problems  still
108       might  have  occurred  on  individual  transfers even when one of these
109       functions return OK.
110

TYPICAL USAGE

112       1. Create a multi handle
113
114       2. Set the socket callback with CURLMOPT_SOCKETFUNCTION(3)
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116       3. Set the timeout callback with CURLMOPT_TIMERFUNCTION(3), to  get  to
117       know what timeout value to use when waiting for socket activities.
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119       4. Add easy handles with curl_multi_add_handle()
120
121       5.  Provide  some  means to manage the sockets libcurl is using, so you
122       can check them for activity. This can be done through your  application
123       code, or by way of an external library such as libevent or glib.
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125       6. Wait for activity on any of libcurl's sockets, use the timeout value
126       your callback has been told
127
128       7, When activity is detected, call curl_multi_socket_action()  for  the
129       socket(s)  that  got action. If no activity is detected and the timeout
130       expires, call curl_multi_socket_action(3) with CURL_SOCKET_TIMEOUT
131
132       8. Go back to step 6.
133

AVAILABILITY

135       This function was added in libcurl 7.15.4, and is deemed  stable  since
136       7.16.0.
137
138       curl_multi_socket(3)  is  deprecated,  use  curl_multi_socket_action(3)
139       instead!
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SEE ALSO

142       curl_multi_cleanup(3),     curl_multi_init(3),     curl_multi_fdset(3),
143       curl_multi_info_read(3), the hiperfifo.c example
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147libcurl 7.61.1                   June 30, 2018            curl_multi_socket(3)
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