1CURLOPT_OPENSOCKETFUNCTION(3c)url_easy_setopt optionCsURLOPT_OPENSOCKETFUNCTION(3)
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6 CURLOPT_OPENSOCKETFUNCTION - callback for opening socket
7
9 #include <curl/curl.h>
10
11 typedef enum {
12 CURLSOCKTYPE_IPCXN, /* socket created for a specific IP connection */
13 } curlsocktype;
14
15 struct curl_sockaddr {
16 int family;
17 int socktype;
18 int protocol;
19 unsigned int addrlen;
20 struct sockaddr addr;
21 };
22
23 curl_socket_t opensocket_callback(void *clientp,
24 curlsocktype purpose,
25 struct curl_sockaddr *address);
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27 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_callback);
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30 Pass a pointer to your callback function, which should match the proto‐
31 type shown above.
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33 This callback function gets called by libcurl instead of the socket(2)
34 call. The callback's purpose argument identifies the exact purpose for
35 this particular socket. CURLSOCKTYPE_IPCXN is for IP based connections
36 and is the only purpose currently used in libcurl. Future versions of
37 libcurl may support more purposes.
38
39 The clientp pointer contains whatever user-defined value set using the
40 CURLOPT_OPENSOCKETDATA(3) function.
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42 The callback gets the resolved peer address as the address argument and
43 is allowed to modify the address or refuse to connect completely. The
44 callback function should return the newly created socket or
45 CURL_SOCKET_BAD in case no connection could be established or another
46 error was detected. Any additional setsockopt(2) calls can of course be
47 done on the socket at the user's discretion. A CURL_SOCKET_BAD return
48 value from the callback function will signal an unrecoverable error to
49 libcurl and it will return CURLE_COULDNT_CONNECT from the function that
50 triggered this callback. This return code can be used for IP address
51 block listing.
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53 If you want to pass in a socket with an already established connection,
54 pass the socket back with this callback and then use CURLOPT_SOCKOPT‐
55 FUNCTION(3) to signal that it already is connected.
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58 The default behavior is the equivalent of this:
59 return socket(addr->family, addr->socktype, addr->protocol);
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62 All
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65 /* make libcurl use the already established socket 'sockfd' */
66
67 static curl_socket_t opensocket(void *clientp,
68 curlsocktype purpose,
69 struct curl_sockaddr *address)
70 {
71 curl_socket_t sockfd;
72 sockfd = *(curl_socket_t *)clientp;
73 /* the actual externally set socket is passed in via the OPENSOCKETDATA
74 option */
75 return sockfd;
76 }
77
78 static int sockopt_callback(void *clientp, curl_socket_t curlfd,
79 curlsocktype purpose)
80 {
81 /* This return code was added in libcurl 7.21.5 */
82 return CURL_SOCKOPT_ALREADY_CONNECTED;
83 }
84
85 curl = curl_easy_init();
86 if(curl) {
87 /* libcurl will internally think that you connect to the host
88 * and port that you specify in the URL option. */
89 curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
90 /* call this function to get a socket */
91 curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
92 curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);
93
94 /* call this function to set options for the socket */
95 curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
96
97 res = curl_easy_perform(curl);
98
99 curl_easy_cleanup(curl);
100 }
101
103 Added in 7.17.1.
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106 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
107 if not.
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110 CURLOPT_OPENSOCKETDATA(3), CURLOPT_SOCKOPTFUNCTION(3), CURLOPT_CLOS‐
111 ESOCKETFUNCTION(3),
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115libcurl 7.85.0 May 17, 2022 CURLOPT_OPENSOCKETFUNCTION(3)