curl/docs/libcurl/curl_easy_send.3

.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at https://curl.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" * SPDX-License-Identifier: curl
.\" *
.\" **************************************************************************
.\"
.TH curl_easy_send 3 "29 April 2008" "libcurl" "libcurl"
.SH NAME
curl_easy_send - sends raw data over an "easy" connection
.SH SYNOPSIS
.nf
#include <curl/easy.h>

CURLcode curl_easy_send(CURL *curl, const void *buffer,
                        size_t buflen, size_t *n);
.fi
.SH DESCRIPTION
This function sends arbitrary data over the established connection. You may
use it together with \fIcurl_easy_recv(3)\fP to implement custom protocols
using libcurl. This functionality can be particularly useful if you use
proxies and/or SSL encryption: libcurl will take care of proxy negotiation and
connection setup.

\fBbuffer\fP is a pointer to the data of length \fBbuflen\fP that you want sent.
The variable \fBn\fP points to will receive the number of sent bytes.

To establish the connection, set \fICURLOPT_CONNECT_ONLY(3)\fP option before
calling \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP. Note that
\fIcurl_easy_send(3)\fP will not work on connections that were created without
this option.

The call will return \fBCURLE_AGAIN\fP if it's not possible to send data right
now - the socket is used in non-blocking mode internally. When
\fBCURLE_AGAIN\fP is returned, use your operating system facilities like
\fIselect(2)\fP to wait until the socket is writable. The socket may be
obtained using \fIcurl_easy_getinfo(3)\fP with \fICURLINFO_ACTIVESOCKET(3)\fP.

Furthermore if you wait on the socket and it tells you it's writable,
\fIcurl_easy_send(3)\fP may return \fBCURLE_AGAIN\fP if the only data that was
sent was for internal SSL processing, and no other data could be sent.
.SH EXAMPLE
.nf
 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
 /* Do not do the transfer - only connect to host */
 curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
 res = curl_easy_perform(curl);

 if(res == CURLE_OK) {
   /* Extract the socket from the curl handle -
      we will need it for waiting. */
   res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);

   /* send data */
   res = curl_easy_send(curl, "hello", 5, &sent);
 }
.fi
.SH AVAILABILITY
Added in 7.18.2.
.SH RETURN VALUE
On success, returns \fBCURLE_OK\fP and stores the number of bytes actually
sent into \fB*n\fP. Note that this may be less than the amount you wanted to
send.

On failure, returns the appropriate error code.

This function may return \fBCURLE_AGAIN\fP. In this case, use your operating
system facilities to wait until the socket is writable, and retry.

If there's no socket available to use from the previous transfer, this function
returns \fBCURLE_UNSUPPORTED_PROTOCOL\fP.
.SH "SEE ALSO"
.BR curl_easy_setopt "(3), " curl_easy_perform "(3), " curl_easy_getinfo "(3), "
.BR curl_easy_recv "(3) "