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afff64dbcd
Follow-up to 82245ea: Fix the example program sendrecv.c (handle
CURLE_AGAIN, handle incomplete send). Improve the documentation
for curl_easy_recv() and curl_easy_send().
Reviewed-by: Frank Meier
Assisted-by: Jay Satiro
See https://github.com/curl/curl/pull/1134
85 lines
3.7 KiB
Groff
85 lines
3.7 KiB
Groff
.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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.\" * are also available at https://curl.haxx.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" **************************************************************************
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.\"
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.TH curl_easy_recv 3 "29 April 2008" "libcurl 7.18.2" "libcurl Manual"
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.SH NAME
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curl_easy_recv - receives raw data on an "easy" connection
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.SH SYNOPSIS
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.B #include <curl/easy.h>
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.sp
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.BI "CURLcode curl_easy_recv( CURL *" curl ", void *" buffer ","
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.BI "size_t " buflen ", size_t *" n ");"
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.ad
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.SH DESCRIPTION
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This function receives raw data from the established connection. You may use
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it together with \fIcurl_easy_send(3)\fP to implement custom protocols using
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libcurl. This functionality can be particularly useful if you use proxies
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and/or SSL encryption: libcurl will take care of proxy negotiation and
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connection set-up.
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\fBbuffer\fP is a pointer to your buffer that will get the received
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data. \fBbuflen\fP is the maximum amount of data you can get in that
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buffer. The variable \fBn\fP points to will receive the number of received
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bytes.
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To establish the connection, set \fICURLOPT_CONNECT_ONLY(3)\fP option before
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calling \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP. Note that
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\fIcurl_easy_recv(3)\fP does not work on connections that were created without
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this option.
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The call will return \fBCURLE_AGAIN\fP if there is no data to read - the
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socket is used in non-blocking mode internally. When \fBCURLE_AGAIN\fP is
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returned, use your operating system facilities like \fIselect(2)\fP to wait
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for data. The socket may be obtained using \fIcurl_easy_getinfo(3)\fP with
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\fICURLINFO_ACTIVESOCKET(3)\fP.
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Wait on the socket only if \fIcurl_easy_recv(3)\fP returns \fBCURLE_AGAIN\fP.
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The reason for this is libcurl or the SSL library may internally cache some
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data, therefore you should call \fIcurl_easy_recv(3)\fP until all data is
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read which would include any cached data.
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Furthermore if you wait on the socket and it tells you there is data to read,
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\fIcurl_easy_recv(3)\fP may return \fBCURLE_AGAIN\fP if the only data that was
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read was for internal SSL processing, and no other data is available.
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.SH AVAILABILITY
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Added in 7.18.2.
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.SH RETURN VALUE
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On success, returns \fBCURLE_OK\fP, stores the received data into
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\fBbuffer\fP, and the number of bytes it actually read into \fB*n\fP.
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On failure, returns the appropriate error code.
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The function may return \fBCURLE_AGAIN\fP. In this case, use your operating
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system facilities to wait until data can be read, and retry.
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Reading exactly 0 bytes indicates a closed connection.
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If there's no socket available to use from the previous transfer, this function
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returns \fBCURLE_UNSUPPORTED_PROTOCOL\fP.
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.SH EXAMPLE
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See \fBsendrecv.c\fP in \fBdocs/examples\fP directory for usage example.
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.SH "SEE ALSO"
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.BR curl_easy_setopt "(3), " curl_easy_perform "(3), "
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.BR curl_easy_getinfo "(3), "
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.BR curl_easy_send "(3) "
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