curl_multi_socket.md

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

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_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

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;
  CURLM *multi;
  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.