CURLMOPT_SOCKETDATA (3) - Linux Manuals
CURLMOPT_SOCKETDATA: custom pointer passed to the socket callback
NAME
CURLMOPT_SOCKETDATA - custom pointer passed to the socket callbackSYNOPSIS
#include <curl/curl.h> CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETDATA, void *pointer);
DESCRIPTION
A data pointer to pass to the socket callback set with the CURLMOPT_SOCKETFUNCTION(3) option.This pointer will not be touched by libcurl but will only be passed in to the socket callbacks's userp argument.