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comparison mupdf-source/thirdparty/curl/docs/libcurl/opts/CURLOPT_SOCKOPTFUNCTION.3 @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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23 .TH CURLOPT_SOCKOPTFUNCTION 3 "16 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
24 .SH NAME
25 CURLOPT_SOCKOPTFUNCTION \- set callback for setting socket options
26 .SH SYNOPSIS
27 .nf
28 #include <curl/curl.h>
29
30 typedef enum {
31 CURLSOCKTYPE_IPCXN, /* socket created for a specific IP connection */
32 CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
33 CURLSOCKTYPE_LAST /* never use */
34 } curlsocktype;
35
36 #define CURL_SOCKOPT_OK 0
37 #define CURL_SOCKOPT_ERROR 1 /* causes libcurl to abort and return
38 CURLE_ABORTED_BY_CALLBACK */
39 #define CURL_SOCKOPT_ALREADY_CONNECTED 2
40
41 int sockopt_callback(void *clientp,
42 curl_socket_t curlfd,
43 curlsocktype purpose);
44
45 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
46 .SH DESCRIPTION
47 Pass a pointer to your callback function, which should match the prototype
48 shown above.
49
50 When set, this callback function gets called by libcurl when the socket has
51 been created, but before the connect call to allow applications to change
52 specific socket options. The callback's \fIpurpose\fP argument identifies the
53 exact purpose for this particular socket:
54
55 \fICURLSOCKTYPE_IPCXN\fP for actively created connections or since 7.28.0
56 \fICURLSOCKTYPE_ACCEPT\fP for FTP when the connection was setup with PORT/EPSV
57 (in earlier versions these sockets weren't passed to this callback).
58
59 Future versions of libcurl may support more purposes. libcurl passes the newly
60 created socket descriptor to the callback in the \fIcurlfd\fP parameter so
61 additional setsockopt() calls can be done at the user's discretion.
62
63 The \fIclientp\fP pointer contains whatever user-defined value set using the
64 \fICURLOPT_SOCKOPTDATA(3)\fP function.
65
66 Return \fICURL_SOCKOPT_OK\fP from the callback on success. Return
67 \fICURL_SOCKOPT_ERROR\fP from the callback function to signal an unrecoverable
68 error to the library and it will close the socket and return
69 \fICURLE_COULDNT_CONNECT\fP.
70 Alternatively, the callback function can return
71 \fICURL_SOCKOPT_ALREADY_CONNECTED\fP, to tell libcurl that the socket is
72 already connected and then libcurl will not attempt to connect it. This allows
73 an application to pass in an already connected socket with
74 \fICURLOPT_OPENSOCKETFUNCTION(3)\fP and then have this function make libcurl
75 not attempt to connect (again).
76 .SH DEFAULT
77 By default, this callback is NULL and unused.
78 .SH PROTOCOLS
79 All
80 .SH EXAMPLE
81 .nf
82 /* make libcurl use the already established socket 'sockfd' */
83
84 static curl_socket_t opensocket(void *clientp,
85 curlsocktype purpose,
86 struct curl_sockaddr *address)
87 {
88 curl_socket_t sockfd;
89 sockfd = *(curl_socket_t *)clientp;
90 /* the actual externally set socket is passed in via the OPENSOCKETDATA
91 option */
92 return sockfd;
93 }
94
95 static int sockopt_callback(void *clientp, curl_socket_t curlfd,
96 curlsocktype purpose)
97 {
98 /* This return code was added in libcurl 7.21.5 */
99 return CURL_SOCKOPT_ALREADY_CONNECTED;
100 }
101
102 curl = curl_easy_init();
103 if(curl) {
104 /* libcurl will internally think that you connect to the host
105 * and port that you specify in the URL option. */
106 curl_easy_setopt(curl, CURLOPT_URL, "http://99.99.99.99:9999");
107 /* call this function to get a socket */
108 curl_easy_setopt(curl, CURLOPT_OPENSOCKETFUNCTION, opensocket);
109 curl_easy_setopt(curl, CURLOPT_OPENSOCKETDATA, &sockfd);
110
111 /* call this function to set options for the socket */
112 curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
113
114 res = curl_easy_perform(curl);
115
116 curl_easy_cleanup(curl);
117 .fi
118 .SH AVAILABILITY
119 Added in 7.16.0. The \fICURL_SOCKOPT_ALREADY_CONNECTED\fP return code was
120 added in 7.21.5.
121 .SH RETURN VALUE
122 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
123 .SH "SEE ALSO"
124 .BR CURLOPT_SOCKOPTDATA "(3), " CURLOPT_OPENSOCKETFUNCTION "(3), "