plucky (3) CURLOPT_SOCKOPTFUNCTION.3.gz

NAME

       CURLOPT_SOCKOPTFUNCTION - callback for setting socket options

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;

       #define CURL_SOCKOPT_OK 0
       #define CURL_SOCKOPT_ERROR 1 /* causes libcurl to abort and return
                                       CURLE_ABORTED_BY_CALLBACK */
       #define CURL_SOCKOPT_ALREADY_CONNECTED 2

       int sockopt_callback(void *clientp,
                            curl_socket_t curlfd,
                            curlsocktype purpose);

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);

DESCRIPTION

       Pass a pointer to your callback function, which should match the prototype shown above.

       When  set, this callback function gets called by libcurl when the socket has been created, but before the
       connect call to allow applications to change specific socket options.  The  callback's  purpose  argument
       identifies the exact purpose for this particular socket:

       CURLSOCKTYPE_IPCXN  for actively created connections or since 7.28.0 CURLSOCKTYPE_ACCEPT for FTP when the
       connection was setup with PORT/EPSV (in earlier versions these sockets were not passed to this callback).

       Future versions of libcurl may support more purposes. libcurl passes the newly created socket  descriptor
       to  the  callback  in  the  curlfd  parameter  so additional setsockopt() calls can be done at the user's
       discretion.

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

       Return CURL_SOCKOPT_OK from the callback on success. Return CURL_SOCKOPT_ERROR from the callback function
       to   signal   an   unrecoverable   error   to   the   library  and  it  closes  the  socket  and  returns
       CURLE_COULDNT_CONNECT. Alternatively, the callback function can return CURL_SOCKOPT_ALREADY_CONNECTED, to
       tell  libcurl  that  the  socket  is  already connected and then libcurl does no attempt to connect. This
       allows an application to pass in an already connected socket with CURLOPT_OPENSOCKETFUNCTION(3) and  then
       have this function make libcurl not attempt to connect (again).

DEFAULT

       NULL

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       /* make libcurl use the already established socket 'sockfd' */

       static curl_socket_t opensocket(void *clientp,
                                       curlsocktype purpose,
                                       struct curl_sockaddr *address)
       {
         curl_socket_t sockfd;
         sockfd = *(curl_socket_t *)clientp;
         /* the actual externally set socket is passed in via the OPENSOCKETDATA
            option */
         return sockfd;
       }

       static int sockopt_callback(void *clientp, curl_socket_t curlfd,
                                   curlsocktype purpose)
       {
         /* This return code was added in libcurl 7.21.5 */
         return CURL_SOCKOPT_ALREADY_CONNECTED;
       }

       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLcode res;
           int sockfd; /* our custom file descriptor */
           /* libcurl thinks that you connect to the host
            * and port that you specify in the URL option. */
           curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
           /* call this function to get a socket */
           curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
           curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);

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

           res = curl_easy_perform(curl);

           curl_easy_cleanup(curl);
         }
       }

AVAILABILITY

       Added in curl 7.16.0

RETURN VALUE

       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).

SEE ALSO

       CURLOPT_OPENSOCKETFUNCTION(3), CURLOPT_SEEKFUNCTION(3), CURLOPT_SOCKOPTDATA(3)