curl_multi_socket(3)

🎀 NAME 🎀

Okay so this is curl_multi_socket from the Library Functions Manual — her whole vibe is read/write available data. 💅

✨ SYNOPSIS ✨

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

🌸 DESCRIPTION 🌸

First things first, bestie: This function is deprecated. Use curl_multi_socket_action(3) instead with ev_bitmask set to 0. 🫶

At return, the integer that 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 🌼

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) instead. No cap, that's the tea. ☕

🦋 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 👑

Go peek at curl_multi_cleanup(3), curl_multi_fdset(3), curl_multi_info_read(3), curl_multi_init(3), and thehiperfifo.cexample. 🔥

xoxo, libcurl 💖 — stamped 2026-10-12 🎀