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90 lines
3.6 KiB
Groff
90 lines
3.6 KiB
Groff
.\" $Id$
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.\"
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.TH curl_multi_socket 3 "21 Dec 2005" "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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#include <curl/curl.h>
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CURLMcode curl_multi_socket(CURLM * multi_handle,
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curl_socket_t sockfd,
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curl_socket_callback callback,
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void *userp);
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CURLMcode curl_multi_socket_all(CURLM *multi_handle,
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curl_socket_callback callback,
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void *userp);
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.SH DESCRIPTION
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Alternative versions of \fIcurl_multi_perform()\fP that allows the application
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to pass in one of the file descriptors/sockets that have been detected to have
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\&"action" on them and let libcurl perform. This allows libcurl to not have to
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scan through all possible file descriptors to check for action. When the
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application has detected on a socket handled by libcurl, call
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\fIcurl_multi_perform()\fP with the \fBsockfd\fP argument set to the socket
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with the action.
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These functions inform the application about updates in the socket (file
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descriptor) status by doing none, one or multiple calls to the
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curl_socket_callback given in the \fBcallback\fP argument. They update the
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status with changes since the previous time this function was used. If
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\fBcallback\fP is NULL, no callback will be called. A status change may also
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be a new timeout only, having the same IN/OUT status as before.
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If you want to force libcurl to (re-)check all its internal sockets and
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transfers instead of just a single one, you call
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\fBcurl_multi_socket_all(3)\fP instead.
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An application should call \fBcurl_multi_timeout(3)\fP to figure out how long
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it should wait for socket actions \- at most \- before doing the timeout
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action: call the \fBcurl_multi_socket(3)\fP function with the \fBsockfd\fP
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argument set to CURL_SOCKET_TIMEOUT.
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\fBcurl_multi_perform(3)\fP is the exact equivalent of calling
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\fBcurl_multi_socket_all\fP(handle, NULL, NULL);
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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" pointer */
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.fi
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The callback MUST return 0.
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The \fIaction\fP (third) 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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.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_perform\fP again, before you select() on more
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actions. You don't have to do it immediately, but the return code means that
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libcurl may have more data available to return or that there may be more data
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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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Call curl_multi_socket_all() first. Setup a "collection" of sockets to
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supervise, then when action happens call curl_multi_socket() for the easy
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handle that got the action.
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.SH AVAILABILITY
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This function was added in libcurl 7.16.0
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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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