CURLMOPT_SOCKETDATA(3)

CURLMOPT_SOCKETDATA3

Custom pointer passed to the socket callback

Usage

#include <curl/curl.h>
CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETDATA, void *pointer);

Overview

A data pointer to pass to the socket callback set with the CURLMOPT_SOCKETFUNCTION(3) option.

This pointer is not touched by libcurl but is only passed in as the socket callback's clientp argument.

Default

NULL

Protocols

This functionality affects all supported protocols

Examples

struct priv {
  void *ours;
};
static int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp)
{
  struct priv *p = sockp;
  printf("my ptr: %p\n", p->ours);
  if(what == CURL_POLL_REMOVE) {
    /* remove the socket from our collection */
  }
  if(what & CURL_POLL_IN) {
    /* wait for read on this socket */
  }
  if(what & CURL_POLL_OUT) {
    /* wait for write on this socket */
  }
  return 0;
}
int main(void)
{
  struct priv setup;
  CURLM *multi = curl_multi_init();
  /* ... use socket callback and custom pointer */
  curl_multi_setopt(multi, CURLMOPT_SOCKETFUNCTION, sock_cb);
  curl_multi_setopt(multi, CURLMOPT_SOCKETDATA, &setup);
}

Return value

Returns CURLM_OK.

Releases

6 releases since Debian 9 (Stretch); the text changed 5 times.

  1. 9
  2. 10
  3. 11
  4. 12
  5. 13
  6. Arch

Availability

Added in curl 7.15.4

From curl 8.23.0-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.