repo/core/curl/files/curl_ws_send.3

.\" generated by cd2nroff 0.1 from curl_ws_send.md
.TH curl_ws_send 3 "2024-08-02" libcurl
.SH NAME
curl_ws_send \- send WebSocket data
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_ws_send(CURL *curl, const void *buffer, size_t buflen,
                      size_t *sent, curl_off_t fragsize,
                      unsigned int flags);
.fi
.SH DESCRIPTION
This function call is EXPERIMENTAL.

Send the specific message fragment over an established WebSocket
connection. The \fIbuffer\fP holds the data to send and it is \fIbuflen\fP
number of payload bytes in that memory area.

\fIsent\fP is returned as the number of payload bytes actually sent.

To send a (huge) fragment using multiple calls with partial content per
invoke, set the \fICURLWS_OFFSET\fP bit and the \fIfragsize\fP argument as the
total expected size for the first part, then set the \fICURLWS_OFFSET\fP with
a zero \fIfragsize\fP for the following parts.

If not sending a partial fragment or if this is raw mode, \fIfragsize\fP
should be set to zero.

If \fBCURLWS_RAW_MODE\fP is enabled in \fICURLOPT_WS_OPTIONS(3)\fP, the
\fBflags\fP argument should be set to 0.

To send a message consisting of multiple frames, set the \fICURLWS_CONT\fP bit
in all frames except the final one.
.SH FLAGS
.IP CURLWS_TEXT
The buffer contains text data. Note that this makes a difference to WebSocket
but libcurl itself does not make any verification of the content or
precautions that you actually send valid UTF\-8 content.
.IP CURLWS_BINARY
This is binary data.
.IP CURLWS_CONT
This is not the final fragment of the message, which implies that there is
another fragment coming as part of the same message where this bit is not set.
.IP CURLWS_CLOSE
Close this transfer.
.IP CURLWS_PING
This is a ping.
.IP CURLWS_PONG
This is a pong.
.IP CURLWS_OFFSET
The provided data is only a partial fragment and there is more coming in a
following call to \fIcurl_ws_send()\fP. When sending only a piece of the
fragment like this, the \fIfragsize\fP must be provided with the total
expected fragment size in the first call and it needs to be zero in subsequent
calls.
.SH PROTOCOLS
This functionality affects ws only
.SH EXAMPLE
.nf
#include <string.h> /* for strlen */

const char *send_payload = "magic";

int main(void)
{
  size_t sent;
  CURLcode res;
  CURL *curl = curl_easy_init();
  curl_easy_setopt(curl, CURLOPT_URL, "wss://example.com/");
  curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 2L);
  curl_easy_perform(curl);
  res = curl_ws_send(curl, send_payload, strlen(send_payload), &sent, 0,
                     CURLWS_PING);
  curl_easy_cleanup(curl);
  return (int)res;
}
.fi
.SH AVAILABILITY
Added in curl 7.86.0
.SH RETURN VALUE
\fICURLE_OK\fP (zero) means that the data was sent properly, non\-zero means an
error occurred as \fI<curl/curl.h>\fP defines. See the \fIlibcurl\-errors(3)\fP man
page for the full list with descriptions.
.SH SEE ALSO
.BR curl_easy_getinfo (3),
.BR curl_easy_perform (3),
.BR curl_easy_setopt (3),
.BR curl_ws_recv (3),
.BR libcurl-ws (3)