CURLOPT_SOCKOPTDATA(3) - Man pages

CURLOPT_SOCKOPTDATA(3)      Library Functions Manual     CURLOPT_SOCKOPTDATA(3)

NAME
       CURLOPT_SOCKOPTDATA - pointer to pass to sockopt callback

SYNOPSIS
       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SOCKOPTDATA, void *pointer);

DESCRIPTION
       Pass  a pointer that is untouched by libcurl and passed as the first ar-
       gument in the sockopt callback set with CURLOPT_SOCKOPTFUNCTION(3).

DEFAULT
       NULL

PROTOCOLS
       This functionality affects all supported protocols

EXAMPLE
       static int sockopt_callback(void *clientp, curl_socket_t curlfd,
                                   curlsocktype purpose)
       {
         int val = *(int *)clientp;
         setsockopt((int)curlfd, SOL_SOCKET, SO_RCVBUF,
                    (const char *)&val, sizeof(val));
         return CURL_SOCKOPT_OK;
       }

       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLcode res;
           int recvbuffersize = 256 * 1024;

           curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");

           /* call this function to set options for the socket */
           curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
           curl_easy_setopt(curl, CURLOPT_SOCKOPTDATA, &recvbuffersize);

           res = curl_easy_perform(curl);

           curl_easy_cleanup(curl);
         }
       }

AVAILABILITY
       Added in curl 7.16.0

RETURN VALUE
       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if
       not.

SEE ALSO
       CURLOPT_OPENSOCKETFUNCTION(3), CURLOPT_SOCKOPTFUNCTION(3)

libcurl                            2026-07-12            CURLOPT_SOCKOPTDATA(3)

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