CURLOPT_OPENSOCKETFUNCTION(3)

1CURLOPT_OPENSOCKETFUNCTION(3c)url_easy_setopt optionCsURLOPT_OPENSOCKETFUNCTION(3)
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NAME

6       CURLOPT_OPENSOCKETFUNCTION - set callback for opening sockets
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SYNOPSIS

9       #include <curl/curl.h>
10
11       typedef enum  {
12         CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
13         CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
14         CURLSOCKTYPE_LAST    /* never use */
15       } curlsocktype;
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17       struct curl_sockaddr {
18         int family;
19         int socktype;
20         int protocol;
21         unsigned int addrlen;
22         struct sockaddr addr;
23       };
24
25       curl_socket_t opensocket_callback(void *clientp,
26                                         curlsocktype purpose,
27                                         struct curl_sockaddr *address);
28
29       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_callback);
30

DESCRIPTION

32       Pass a pointer to your callback function, which should match the proto‐
33       type shown above.
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35       This callback function gets called by libcurl instead of the  socket(2)
36       call.  The callback's purpose argument identifies the exact purpose for
37       this particular socket: CURLSOCKTYPE_IPCXN is for IP based  connections
38       and CURLSOCKTYPE_ACCEPT is for sockets created after accept() - such as
39       when doing active FTP. Future versions of libcurl may support more pur‐
40       poses.
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42       The  clientp pointer contains whatever user-defined value set using the
43       CURLOPT_OPENSOCKETDATA(3) function.
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45       The callback gets the resolved peer address as the address argument and
46       is  allowed  to modify the address or refuse to connect completely. The
47       callback  function  should  return  the   newly   created   socket   or
48       CURL_SOCKET_BAD  in  case no connection could be established or another
49       error was detected. Any additional setsockopt(2) calls can of course be
50       done  on the socket at the user's discretion.  A CURL_SOCKET_BAD return
51       value from the callback function will signal an unrecoverable error  to
52       libcurl and it will return CURLE_COULDNT_CONNECT from the function that
53       triggered this callback.  This return code can be used for  IP  address
54       blacklisting.
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56       If you want to pass in a socket with an already established connection,
57       pass the socket back with this callback and then  use  CURLOPT_SOCKOPT‐
58       FUNCTION(3) to signal that it already is connected.
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DEFAULT

61       The default behavior is the equivalent of this:
62          return socket(addr->family, addr->socktype, addr->protocol);
63

PROTOCOLS

65       All
66

EXAMPLE

68       /* make libcurl use the already established socket 'sockfd' */
69
70       static curl_socket_t opensocket(void *clientp,
71                                       curlsocktype purpose,
72                                       struct curl_sockaddr *address)
73       {
74         curl_socket_t sockfd;
75         sockfd = *(curl_socket_t *)clientp;
76         /* the actual externally set socket is passed in via the OPENSOCKETDATA
77            option */
78         return sockfd;
79       }
80
81       static int sockopt_callback(void *clientp, curl_socket_t curlfd,
82                                   curlsocktype purpose)
83       {
84         /* This return code was added in libcurl 7.21.5 */
85         return CURL_SOCKOPT_ALREADY_CONNECTED;
86       }
87
88       curl = curl_easy_init();
89       if(curl) {
90         /* libcurl will internally think that you connect to the host
91          * and port that you specify in the URL option. */
92         curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
93         /* call this function to get a socket */
94         curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
95         curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);
96
97         /* call this function to set options for the socket */
98         curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
99
100         res = curl_easy_perform(curl);
101
102         curl_easy_cleanup(curl);
103       }
104

AVAILABILITY

106       Added in 7.17.1.
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RETURN VALUE

109       Returns  CURLE_OK  if the option is supported, and CURLE_UNKNOWN_OPTION
110       if not.
111