CURLOPT_OPENSOCKETFUNCTION(curl_easy_setopt optioCURLOPT_OPENSOCKETFUNCTION(3)

NAME
       CURLOPT_OPENSOCKETFUNCTION - set callback for opening sockets

SYNOPSIS
       #include <curl/curl.h>

       typedef enum  {
         CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
         CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
         CURLSOCKTYPE_LAST    /* never use */
       } curlsocktype;

       struct curl_sockaddr {
         int family;
         int socktype;
         int protocol;
         unsigned int addrlen;
         struct sockaddr addr;
       };

       curl_socket_t opensocket_callback(void *clientp,
                                         curlsocktype purpose,
                                         struct curl_sockaddr *address);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_callback);

DESCRIPTION
       Pass a pointer to your callback function, which should match the proto-
       type shown above.

       This callback function gets called by libcurl instead of the  socket(2)
       call.  The callback's purpose argument identifies the exact purpose for
       this particular socket: CURLSOCKTYPE_IPCXN is for IP based  connections
       and CURLSOCKTYPE_ACCEPT is for sockets created after accept() - such as
       when doing active FTP. Future versions of libcurl may support more pur-
       poses.

       The  clientp pointer contains whatever user-defined value set using the
       CURLOPT_OPENSOCKETDATA(3) function.

       The callback gets the resolved peer address as the address argument and
       is  allowed  to modify the address or refuse to connect completely. The
       callback  function  should  return  the   newly   created   socket   or
       CURL_SOCKET_BAD  in  case no connection could be established or another
       error was detected. Any additional setsockopt(2) calls can of course be
       done  on the socket at the user's discretion.  A CURL_SOCKET_BAD return
       value from the callback function will signal an unrecoverable error  to
       libcurl and it will return CURLE_COULDNT_CONNECT from the function that
       triggered this callback.  This return code can be used for  IP  address
       blacklisting.

       If you want to pass in a socket with an already established connection,
       pass the socket back with this callback and then  use  CURLOPT_SOCKOPT-
       FUNCTION(3) to signal that it already is connected.

DEFAULT
       The default behavior is the equivalent of this:
          return socket(addr->family, addr->socktype, addr->protocol);

PROTOCOLS
       All

EXAMPLE
AVAILABILITY
       Added in 7.17.1.

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

SEE ALSO
       CURLOPT_OPENSOCKETDATA(3),  CURLOPT_SOCKOPTFUNCTION(3),   CURLOPT_CLOS-
       ESOCKETFUNCTION(3),

libcurl 7.54.0                 February 03, 2016 CURLOPT_OPENSOCKETFUNCTION(3)