136 lines
3.4 KiB
Markdown
136 lines
3.4 KiB
Markdown
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---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLMOPT_SOCKETFUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLMOPT_SOCKETDATA (3)
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- CURLMOPT_TIMERFUNCTION (3)
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- curl_multi_socket_action (3)
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---
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# NAME
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CURLMOPT_SOCKETFUNCTION - callback informed about what to wait for
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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int socket_callback(CURL *easy, /* easy handle */
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curl_socket_t s, /* socket */
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int what, /* describes the socket */
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void *clientp, /* private callback pointer */
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void *socketp); /* private socket pointer */
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CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETFUNCTION, socket_callback);
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~~~
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# DESCRIPTION
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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When the curl_multi_socket_action(3) function is called, it uses this
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callback to inform the application about updates in the socket (file
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descriptor) status by doing none, one, or multiple calls to the
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**socket_callback**. The callback function gets status updates with changes
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since the previous time the callback was called. If the given callback pointer
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is set to NULL, no callback is called.
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libcurl then expects the application to monitor the sockets for the specific
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activities and tell libcurl again when something happens on one of them. Tell
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libcurl by calling curl_multi_socket_action(3).
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# CALLBACK ARGUMENTS
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*easy* identifies the specific transfer for which this update is related.
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*s* is the specific socket this function invocation concerns. If the
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**what** argument is not CURL_POLL_REMOVE then it holds information about
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what activity on this socket the application is supposed to
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monitor. Subsequent calls to this callback might update the **what** bits
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for a socket that is already monitored.
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The socket callback should return 0 on success, and -1 on error. If this
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callback returns error, **all** transfers currently in progress in this
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multi handle are aborted and made to fail.
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**clientp** is set with CURLMOPT_SOCKETDATA(3).
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**socketp** is set with curl_multi_assign(3) or NULL.
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The **what** parameter informs the callback on the status of the given
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socket. It can hold one of these values:
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## CURL_POLL_IN
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Wait for incoming data. For the socket to become readable.
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## CURL_POLL_OUT
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Wait for outgoing data. For the socket to become writable.
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## CURL_POLL_INOUT
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Wait for incoming and outgoing data. For the socket to become readable or
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writable.
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## CURL_POLL_REMOVE
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The specified socket/file descriptor is no longer used by libcurl for any
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active transfer. It might soon be added again.
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# DEFAULT
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NULL (no callback)
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# PROTOCOLS
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All
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# EXAMPLE
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~~~c
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struct priv {
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void *ours;
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};
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static int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp)
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{
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struct priv *p = sockp;
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printf("our ptr: %p\n", p->ours);
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if(what == CURL_POLL_REMOVE) {
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/* remove the socket from our collection */
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}
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if(what & CURL_POLL_IN) {
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/* wait for read on this socket */
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}
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if(what & CURL_POLL_OUT) {
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/* wait for write on this socket */
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}
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return 0;
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}
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int main(void)
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{
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struct priv setup;
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CURLM *multi = curl_multi_init();
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/* ... use socket callback and custom pointer */
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curl_multi_setopt(multi, CURLMOPT_SOCKETFUNCTION, sock_cb);
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curl_multi_setopt(multi, CURLMOPT_SOCKETDATA, &setup);
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}
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~~~
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# AVAILABILITY
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Added in 7.15.4
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# RETURN VALUE
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Returns CURLM_OK.
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