Annotation of embedaddon/curl/docs/libcurl/opts/CURLOPT_SOCKOPTFUNCTION.3, revision 1.1.1.1
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23: .TH CURLOPT_SOCKOPTFUNCTION 3 "May 15, 2017" "libcurl 7.70.0" "curl_easy_setopt options"
24:
25: .SH NAME
26: CURLOPT_SOCKOPTFUNCTION \- set callback for setting socket options
27: .SH SYNOPSIS
28: .nf
29: #include <curl/curl.h>
30:
31: typedef enum {
32: CURLSOCKTYPE_IPCXN, /* socket created for a specific IP connection */
33: CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
34: CURLSOCKTYPE_LAST /* never use */
35: } curlsocktype;
36:
37: #define CURL_SOCKOPT_OK 0
38: #define CURL_SOCKOPT_ERROR 1 /* causes libcurl to abort and return
39: CURLE_ABORTED_BY_CALLBACK */
40: #define CURL_SOCKOPT_ALREADY_CONNECTED 2
41:
42: int sockopt_callback(void *clientp,
43: curl_socket_t curlfd,
44: curlsocktype purpose);
45:
46: CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
47: .SH DESCRIPTION
48: Pass a pointer to your callback function, which should match the prototype
49: shown above.
50:
51: When set, this callback function gets called by libcurl when the socket has
52: been created, but before the connect call to allow applications to change
53: specific socket options. The callback's \fIpurpose\fP argument identifies the
54: exact purpose for this particular socket:
55:
56: \fICURLSOCKTYPE_IPCXN\fP for actively created connections or since 7.28.0
57: \fICURLSOCKTYPE_ACCEPT\fP for FTP when the connection was setup with PORT/EPSV
58: (in earlier versions these sockets weren't passed to this callback).
59:
60: Future versions of libcurl may support more purposes. libcurl passes the newly
61: created socket descriptor to the callback in the \fIcurlfd\fP parameter so
62: additional setsockopt() calls can be done at the user's discretion.
63:
64: The \fIclientp\fP pointer contains whatever user-defined value set using the
65: \fICURLOPT_SOCKOPTDATA(3)\fP function.
66:
67: Return \fICURL_SOCKOPT_OK\fP from the callback on success. Return
68: \fICURL_SOCKOPT_ERROR\fP from the callback function to signal an unrecoverable
69: error to the library and it will close the socket and return
70: \fICURLE_COULDNT_CONNECT\fP.
71: Alternatively, the callback function can return
72: \fICURL_SOCKOPT_ALREADY_CONNECTED\fP, to tell libcurl that the socket is
73: already connected and then libcurl will not attempt to connect it. This allows
74: an application to pass in an already connected socket with
75: \fICURLOPT_OPENSOCKETFUNCTION(3)\fP and then have this function make libcurl
76: not attempt to connect (again).
77: .SH DEFAULT
78: By default, this callback is NULL and unused.
79: .SH PROTOCOLS
80: All
81: .SH EXAMPLE
82: .nf
83: /* make libcurl use the already established socket 'sockfd' */
84:
85: static curl_socket_t opensocket(void *clientp,
86: curlsocktype purpose,
87: struct curl_sockaddr *address)
88: {
89: curl_socket_t sockfd;
90: sockfd = *(curl_socket_t *)clientp;
91: /* the actual externally set socket is passed in via the OPENSOCKETDATA
92: option */
93: return sockfd;
94: }
95:
96: static int sockopt_callback(void *clientp, curl_socket_t curlfd,
97: curlsocktype purpose)
98: {
99: /* This return code was added in libcurl 7.21.5 */
100: return CURL_SOCKOPT_ALREADY_CONNECTED;
101: }
102:
103: curl = curl_easy_init();
104: if(curl) {
105: /* libcurl will internally think that you connect to the host
106: * and port that you specify in the URL option. */
107: curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
108: /* call this function to get a socket */
109: curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
110: curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);
111:
112: /* call this function to set options for the socket */
113: curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
114:
115: res = curl_easy_perform(curl);
116:
117: curl_easy_cleanup(curl);
118: .fi
119: .SH AVAILABILITY
120: Added in 7.16.0. The \fICURL_SOCKOPT_ALREADY_CONNECTED\fP return code was
121: added in 7.21.5.
122: .SH RETURN VALUE
123: Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
124: .SH "SEE ALSO"
125: .BR CURLOPT_SOCKOPTDATA "(3), " CURLOPT_OPENSOCKETFUNCTION "(3), "
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