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23 .TH CURLOPT_OPENSOCKETFUNCTION 3 "May 15, 2017" "libcurl 7.56.1" "curl_easy_setopt options"
26 CURLOPT_OPENSOCKETFUNCTION \- set callback for opening sockets
29 #include <curl/curl.h>
32 CURLSOCKTYPE_IPCXN, /* socket created for a specific IP connection */
33 CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
34 CURLSOCKTYPE_LAST /* never use */
37 struct curl_sockaddr {
45 curl_socket_t opensocket_callback(void *clientp,
47 struct curl_sockaddr *address);
49 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_OPENSOCKETFUNCTION, opensocket_callback);
51 Pass a pointer to your callback function, which should match the prototype
54 This callback function gets called by libcurl instead of the \fIsocket(2)\fP
55 call. The callback's \fIpurpose\fP argument identifies the exact purpose for
56 this particular socket: \fICURLSOCKTYPE_IPCXN\fP is for IP based connections
57 and \fICURLSOCKTYPE_ACCEPT\fP is for sockets created after accept() - such as
58 when doing active FTP. Future versions of libcurl may support more
61 The \fIclientp\fP pointer contains whatever user-defined value set using the
62 \fICURLOPT_OPENSOCKETDATA(3)\fP function.
64 The callback gets the resolved peer address as the \fIaddress\fP argument and
65 is allowed to modify the address or refuse to connect completely. The callback
66 function should return the newly created socket or \fICURL_SOCKET_BAD\fP in
67 case no connection could be established or another error was detected. Any
68 additional \fIsetsockopt(2)\fP calls can of course be done on the socket at
69 the user's discretion. A \fICURL_SOCKET_BAD\fP return value from the callback
70 function will signal an unrecoverable error to libcurl and it will return
71 \fICURLE_COULDNT_CONNECT\fP from the function that triggered this callback.
72 This return code can be used for IP address blacklisting.
74 If you want to pass in a socket with an already established connection, pass
75 the socket back with this callback and then use
76 \fICURLOPT_SOCKOPTFUNCTION(3)\fP to signal that it already is connected.
78 The default behavior is the equivalent of this:
80 return socket(addr->family, addr->socktype, addr->protocol);
86 /* make libcurl use the already established socket 'sockfd' */
88 static curl_socket_t opensocket(void *clientp,
90 struct curl_sockaddr *address)
93 sockfd = *(curl_socket_t *)clientp;
94 /* the actual externally set socket is passed in via the OPENSOCKETDATA
99 static int sockopt_callback(void *clientp, curl_socket_t curlfd,
100 curlsocktype purpose)
102 /* This return code was added in libcurl 7.21.5 */
103 return CURL_SOCKOPT_ALREADY_CONNECTED;
106 curl = curl_easy_init();
108 /* libcurl will internally think that you connect to the host
109 * and port that you specify in the URL option. */
110 curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
111 /* call this function to get a socket */
112 curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
113 curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);
115 /* call this function to set options for the socket */
116 curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
118 res = curl_easy_perform(curl);
120 curl_easy_cleanup(curl);
126 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
128 .BR CURLOPT_OPENSOCKETDATA "(3), " CURLOPT_SOCKOPTFUNCTION "(3), "
129 .BR CURLOPT_CLOSESOCKETFUNCTION "(3), "