---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: curl_multi_socket
Section: 3
Source: libcurl
See-also:
  - curl_multi_cleanup (3)
  - curl_multi_fdset (3)
  - curl_multi_info_read (3)
  - curl_multi_init (3)
  - the hiperfifo.c example
Protocol:
  - All
Added-in: 7.15.4
---

# NAME

curl_multi_socket - read/write available data

# SYNOPSIS

~~~c
#include <curl/curl.h>
CURLMcode curl_multi_socket(CURLM *multi_handle, curl_socket_t sockfd,
                            int *running_handles);
~~~

# DESCRIPTION

This function is deprecated. Use curl_multi_socket_action(3) instead with
**ev_bitmask** set to 0.

At return, the integer **running_handles** points to contains 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(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(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(3) 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(3) option with
curl_multi_setopt(3). Your application then gets 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.

# %PROTOCOLS%

# EXAMPLE

~~~c
int main(void)
{
  /* the event-library gets told when there activity on the socket 'fd',
     which we translate to a call to curl_multi_socket_action() */
  int running;
  int rc;
  int fd = 2;
  CURLM *multi = curl_multi_init();

  rc = curl_multi_socket(multi, fd, &running);
}
~~~

# DEPRECATED

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

# %AVAILABILITY%

# RETURN VALUE

This function returns a CURLMcode indicating success or error.

CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
libcurl-errors(3).

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.
