curl_multi_socket(3) Library Functions Manual curl_multi_socket(3)
NAME
curl_multi_socket - read/write available data
SYNOPSIS
#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_SOCKETFUNC-
TION(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 infor-
mation 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
This functionality affects all supported protocols
EXAMPLE
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) in-
stead.
AVAILABILITY
Added in curl 7.15.4
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.
SEE ALSO
curl_multi_cleanup(3), curl_multi_fdset(3), curl_multi_info_read(3),
curl_multi_init(3), thehiperfifo.cexample
libcurl 2026-07-12 curl_multi_socket(3)
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