curl_multi_socket.3 6.7 KB

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  22. .TH curl_multi_socket 3 "9 Jul 2006" "libcurl 7.16.0" "libcurl Manual"
  23. .SH NAME
  24. curl_multi_socket \- reads/writes available data
  25. .SH SYNOPSIS
  26. .nf
  27. #include <curl/curl.h>
  28. CURLMcode curl_multi_socket(CURLM * multi_handle, curl_socket_t sockfd,
  29. int *running_handles);
  30. CURLMcode curl_multi_socket_all(CURLM *multi_handle,
  31. int *running_handles);
  32. .fi
  33. .SH DESCRIPTION
  34. These functions are deprecated. Do not use! See
  35. \fIcurl_multi_socket_action(3)\fP instead!
  36. At return, the integer \fBrunning_handles\fP points to will contain the number
  37. of still running easy handles within the multi handle. When this number
  38. reaches zero, all transfers are complete/done. Note that when you call
  39. \fIcurl_multi_socket_action(3)\fP on a specific socket and the counter
  40. decreases by one, it DOES NOT necessarily mean that this exact socket/transfer
  41. is the one that completed. Use \fIcurl_multi_info_read(3)\fP to figure out
  42. which easy handle that completed.
  43. The \fIcurl_multi_socket_action(3)\fP functions inform the application about
  44. updates in the socket (file descriptor) status by doing none, one, or multiple
  45. calls to the socket callback function set with the
  46. \fICURLMOPT_SOCKETFUNCTION(3)\fP option to \fIcurl_multi_setopt(3)\fP. They
  47. update the status with changes since the previous time the callback was
  48. called.
  49. Get the timeout time by setting the \fICURLMOPT_TIMERFUNCTION(3)\fP option
  50. with \fIcurl_multi_setopt(3)\fP. Your application will then get called with
  51. information on how long to wait for socket actions at most before doing the
  52. timeout action: call the \fIcurl_multi_socket_action(3)\fP function with the
  53. \fBsockfd\fP argument set to CURL_SOCKET_TIMEOUT. You can also use the
  54. \fIcurl_multi_timeout(3)\fP function to poll the value at any given time, but
  55. for an event-based system using the callback is far better than relying on
  56. polling the timeout value.
  57. Usage of \fIcurl_multi_socket(3)\fP is deprecated, whereas the function is
  58. equivalent to \fIcurl_multi_socket_action(3)\fP with \fBev_bitmask\fP set to
  59. 0.
  60. Force libcurl to (re-)check all its internal sockets and transfers instead of
  61. just a single one by calling \fIcurl_multi_socket_all(3)\fP. Note that there
  62. should not be any reason to use this function!
  63. .SH "CALLBACK DETAILS"
  64. The socket \fBcallback\fP function uses a prototype like this
  65. .nf
  66. int curl_socket_callback(CURL *easy, /* easy handle */
  67. curl_socket_t s, /* socket */
  68. int action, /* see values below */
  69. void *userp, /* private callback pointer */
  70. void *socketp); /* private socket pointer */
  71. .fi
  72. The callback MUST return 0.
  73. The \fIeasy\fP argument is a pointer to the easy handle that deals with this
  74. particular socket. Note that a single handle may work with several sockets
  75. simultaneously.
  76. The \fIs\fP argument is the actual socket value as you use it within your
  77. system.
  78. The \fIaction\fP argument to the callback has one of five values:
  79. .RS
  80. .IP "CURL_POLL_NONE (0)"
  81. register, not interested in readiness (yet)
  82. .IP "CURL_POLL_IN (1)"
  83. register, interested in read readiness
  84. .IP "CURL_POLL_OUT (2)"
  85. register, interested in write readiness
  86. .IP "CURL_POLL_INOUT (3)"
  87. register, interested in both read and write readiness
  88. .IP "CURL_POLL_REMOVE (4)"
  89. unregister
  90. .RE
  91. The \fIsocketp\fP argument is a private pointer you have previously set with
  92. \fIcurl_multi_assign(3)\fP to be associated with the \fIs\fP socket. If no
  93. pointer has been set, socketp will be NULL. This argument is of course a
  94. service to applications that want to keep certain data or structs that are
  95. strictly associated to the given socket.
  96. The \fIuserp\fP argument is a private pointer you have previously set with
  97. \fIcurl_multi_setopt(3)\fP and the \fICURLMOPT_SOCKETDATA(3)\fP option.
  98. .SH "RETURN VALUE"
  99. CURLMcode type, general libcurl multi interface error code.
  100. Legacy: If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this basically means
  101. that you should call \fIcurl_multi_socket(3)\fP again, before you wait for
  102. more actions on libcurl's sockets. You don't have to do it immediately, but
  103. the return code means that libcurl may have more data available to return or
  104. that there may be more data to send off before it is "satisfied".
  105. In modern libcurls, \fICURLM_CALL_MULTI_PERFORM\fP or
  106. \fICURLM_CALL_MULTI_SOCKET\fP should not be returned and no application needs
  107. to care about them.
  108. NOTE that the return code is for the whole multi stack. Problems still might have
  109. occurred on individual transfers even when one of these functions
  110. return OK.
  111. .SH "TYPICAL USAGE"
  112. 1. Create a multi handle
  113. 2. Set the socket callback with \fICURLMOPT_SOCKETFUNCTION(3)\fP
  114. 3. Set the timeout callback with \fICURLMOPT_TIMERFUNCTION(3)\fP, to get to
  115. know what timeout value to use when waiting for socket activities.
  116. 4. Add easy handles with curl_multi_add_handle()
  117. 5. Provide some means to manage the sockets libcurl is using, so you can check
  118. them for activity. This can be done through your application code, or by way
  119. of an external library such as libevent or glib.
  120. 6. Wait for activity on any of libcurl's sockets, use the timeout value your
  121. callback has been told
  122. 7, When activity is detected, call curl_multi_socket_action() for the
  123. socket(s) that got action. If no activity is detected and the timeout expires,
  124. call \fIcurl_multi_socket_action(3)\fP with \fICURL_SOCKET_TIMEOUT\fP
  125. 8. Go back to step 6.
  126. .SH AVAILABILITY
  127. This function was added in libcurl 7.15.4, and is deemed stable since
  128. 7.16.0.
  129. \fIcurl_multi_socket(3)\fP is deprecated, use
  130. \fIcurl_multi_socket_action(3)\fP instead!
  131. .SH "SEE ALSO"
  132. .BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
  133. .BR curl_multi_fdset "(3), " curl_multi_info_read "(3), "
  134. .BR "the hiperfifo.c example"