CURLOPT_CLOSESOCKETDATA - pointer passed to the socket close callback

Added in curl 7.21.7

NULL

Pass a pointer that remains untouched by libcurl and passed as the first argument in the closesocket callback set with CURLOPT_CLOSESOCKETFUNCTION(3).

struct priv { void *custom; }; static int closesocket(void *clientp, curl_socket_t item) { struct priv *my = clientp; printf("our ptr: %p\n", my->custom); printf("libcurl wants to close %d now\n", (int)item); return 0; } int main(void) { struct priv myown; CURL *curl = curl_easy_init(); /* call this function to close sockets */ curl_easy_setopt(curl, CURLOPT_CLOSESOCKETFUNCTION, closesocket); curl_easy_setopt(curl, CURLOPT_CLOSESOCKETDATA, &myown); curl_easy_perform(curl); curl_easy_cleanup(curl); }

CURLOPT_CLOSESOCKETDATA - pointer passed to the socket close callback

This functionality affects all supported protocols

curl_easy_setopt(3) returns a CURLcode indicating success or error. CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

CURLOPT_CLOSESOCKETFUNCTION(3), CURLOPT_OPENSOCKETFUNCTION(3) libcurl 2025-06-16 CURLOPT_CLOSESOCKETDATA(3)

#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CLOSESOCKETDATA, void *pointer);