---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLMOPT_SOCKETDATA
Section: 3
Source: libcurl
See-also:
  - CURLMOPT_SOCKETFUNCTION (3)
  - CURLMOPT_TIMERFUNCTION (3)
  - curl_multi_socket_action (3)
Protocol:
  - All
---

# NAME

CURLMOPT_SOCKETDATA - custom pointer passed to the socket callback

# SYNOPSIS

~~~c
#include <curl/curl.h>

CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETDATA, void *pointer);
~~~

# DESCRIPTION

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

# EXAMPLE

~~~c
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);
}
~~~

# AVAILABILITY

Added in 7.15.4

# RETURN VALUE

Returns CURLM_OK.