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151 lines
6.2 KiB
Groff
151 lines
6.2 KiB
Groff
.\" $Id$
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.\"
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.TH curl_multi_socket 3 "9 Jul 2006" "libcurl 7.16.0" "libcurl Manual"
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.SH NAME
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curl_multi_socket \- reads/writes available data
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLMcode curl_multi_socket_action(CURLM * multi_handle,
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curl_socket_t sockfd, int ev_bitmask,
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int *running_handles);
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CURLMcode curl_multi_socket(CURLM * multi_handle, curl_socket_t sockfd,
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int *running_handles);
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CURLMcode curl_multi_socket_all(CURLM *multi_handle,
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int *running_handles);
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.fi
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.SH DESCRIPTION
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Alternative versions of \fIcurl_multi_perform(3)\fP that allows the
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application to pass in the file descriptor/socket that has been detected to
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have \&"action" on it and let libcurl perform. This allows libcurl to not have
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to scan through all possible file descriptors to check for action. When the
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application has detected action on a socket handled by libcurl, it should call
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\fIcurl_multi_socket_action(3)\fP with the \fBsockfd\fP argument set to the
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socket with the action. When the events on a socket are known, they can be
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passed as an events bitmask \fBev_bitmask\fP by first setting \fBev_bitmask\fP
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to 0, and then adding using bitwise OR (|) any combination of events to be
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choosen from CURL_CSELECT_IN, CURL_CSELECT_OUT or CURL_CSELECT_ERR. When the
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events on a socket are unknown, pass 0 instead, and libcurl will test the
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descriptor internally.
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At return, the int \fBrunning_handles\fP points to will contain the number of
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still running easy handles within the multi handle. When this number reaches
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zero, all transfers are complete/done. Note that when you call
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\fIcurl_multi_socket_action(3)\fP on a specific socket and the counter
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decreases by one, it DOES NOT necessarily mean that this exact socket/transfer
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is the one that completed. Use \fIcurl_multi_info_read(3)\fP to figure out
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which easy handle that completed.
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The curl_multi_socket functions inform the application about updates in the
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socket (file descriptor) status by doing none, one or multiple calls to the
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socket callback function set with the CURLMOPT_SOCKETFUNCTION option to
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\fIcurl_multi_setopt(3)\fP. They update the status with changes since the
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previous time this function was called.
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To force libcurl to (re-)check all its internal sockets and transfers instead
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of just a single one, you call \fBcurl_multi_socket_all(3)\fP. This is
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typically done as the first function call before the application has any
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knowledge about what sockets libcurl uses.
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Applications should call \fBcurl_multi_timeout(3)\fP to figure out how long to
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wait for socket actions \- at most \- before doing the timeout action: call
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the \fBcurl_multi_socket(3)\fP function with the \fBsockfd\fP argument set to
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CURL_SOCKET_TIMEOUT.
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Usage of \fIcurl_multi_socket(3)\fP is depricated, whereas the function is
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equivalent to \fIcurl_multi_socket_action(3)\fP, when \fBev_bitmask\fP is set
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to 0.
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.SH "CALLBACK DETAILS"
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The socket \fBcallback\fP function uses a prototype like this
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.nf
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int curl_socket_callback(CURL *easy, /* easy handle */
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curl_socket_t s, /* socket */
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int action, /* see values below */
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void *userp, /* private callback pointer */
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void *socketp); /* private socket pointer */
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.fi
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The callback MUST return 0.
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The \fIeasy\fP argument is a pointer to the easy handle that deals with this
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particular socket. Note that a single handle may work with several sockets
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simultaneously.
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The \fIs\fP argument is the actual socket value as you use it within your
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system.
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The \fIaction\fP argument to the callback has one of five values:
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.RS
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.IP "CURL_POLL_NONE (0)"
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register, not interested in readiness (yet)
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.IP "CURL_POLL_IN (1)"
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register, interested in read readiness
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.IP "CURL_POLL_OUT (2)"
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register, interested in write readiness
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.IP "CURL_POLL_INOUT (3)"
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register, interested in both read and write readiness
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.IP "CURL_POLL_REMOVE (4)"
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deregister
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.RE
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The \fIsocketp\fP argument is a private pointer you have previously set with
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\fIcurl_multi_assign(3)\fP to be associated with the \fIs\fP socket. If no
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pointer has been set, socketp will be NULL. This argument is of course a
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service to applications that want to keep certain data or structs that are
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strictly associated to the given socket.
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The \fIuserp\fP argument is a private pointer you have previously set with
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\fIcurl_multi_setopt(3)\fP and the CURLMOPT_SOCKETDATA option.
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.SH "RETURN VALUE"
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CURLMcode type, general libcurl multi interface error code.
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If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this basically means that you
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should call \fIcurl_multi_socket(3)\fP again, before you wait for more actions
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on libcurl's sockets. You don't have to do it immediately, but the return code
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means that libcurl may have more data available to return or that there may be
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more data to send off before it is "satisfied".
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NOTE that this only returns errors etc regarding the whole multi stack. There
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might still have occurred problems on individual transfers even when this
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function returns OK.
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.SH "TYPICAL USAGE"
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1. Create a multi handle
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2. Set the socket callback with CURLMOPT_SOCKETFUNCTION
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3. Set the timeout callback with CURLMOPT_TIMERFUNCTION, to get to know what
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timeout value to use when waiting for socket activities.
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4. Add easy handles
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5. Call curl_multi_socket_all() first once
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6. Provide some means to manage the sockets libcurl is using, so you can check
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them for activity. This can be done through your application code, or by way
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of an external library such as libevent or glib.
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7. Wait for activity on any of libcurl's sockets, use the timeout value your
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calback has been told
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8, When activity is detected, call curl_multi_socket_action() for the
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socket(s) that got action. If no activity is detected and the timeout expires,
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call \fIcurl_multi_socket(3)\fP with \fICURL_SOCKET_TIMEOUT\fP
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9. Go back to step 7.
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.SH AVAILABILITY
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This function was added in libcurl 7.15.4, although deemed stable since
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7.16.0.
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\fIcurl_multi_socket(3)\fP is deprecated, use
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\fIcurl_multi_socket_action(3)\fP instead!
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.SH "SEE ALSO"
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.BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
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.BR curl_multi_fdset "(3), " curl_multi_info_read "(3), "
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.BR "the hiperfifo.c example"
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