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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
       /* 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;
       }

       curl = curl_easy_init();
       if(curl)	{
	 /* libcurl will internally think 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	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	7.54.1			 May 15, 2017	 CURLOPT_OPENSOCKETFUNCTION(3)

NAME | SYNOPSIS | DESCRIPTION | DEFAULT | PROTOCOLS | EXAMPLE | AVAILABILITY | RETURN VALUE | SEE ALSO

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