---
name: "curl_ws_send"
section: "3"
platform: "macos"
package: "curl"
version: "166.0.0.0.1"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/curl_ws_send"
---

# curl\_ws\_send(3)

send WebSocket data

## NAME

curl\_ws\_send - send WebSocket data

## SYNOPSIS

```
#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);
```

## DESCRIPTION

This function call is EXPERIMENTAL.

Send the specific message fragment over an established WebSocket connection. The *buffer* holds the data to send and it is *buflen* number of payload bytes in that memory area.

*sent* 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 *CURLWS\_OFFSET* bit and the *fragsize* argument as the total expected size for the first part, then set the *CURLWS\_OFFSET* with a zero *fragsize* for the following parts.

If not sending a partial fragment or if this is raw mode, *fragsize* should be set to zero.

If **CURLWS\_RAW\_MODE** is enabled in *[CURLOPT\_WS\_OPTIONS(3)](/CURLOPT_WS_OPTIONS/3.md)*, the **flags** argument should be set to 0.

To send a message consisting of multiple frames, set the *CURLWS\_CONT* bit in all frames except the final one.

## FLAGS

- 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.

- CURLWS\_BINARY

  This is binary data.

- 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.

- CURLWS\_CLOSE

  Close this transfer.

- CURLWS\_PING

  This is a ping.

- CURLWS\_PONG

  This is a pong.

- CURLWS\_OFFSET

  The provided data is only a partial fragment and there is more coming in a following call to *curl\_ws\_send()*. When sending only a piece of the fragment like this, the *fragsize* must be provided with the total expected fragment size in the first call and it needs to be zero in subsequent calls.

## EXAMPLE

```
#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;
}
```

## AVAILABILITY

Added in 7.86.0.

## RETURN VALUE

*CURLE\_OK* (zero) means that the data was sent properly, non-zero means an error occurred as *\<curl/curl.h\>* defines. See the *[libcurl-errors(3)](/libcurl-errors/3.md)* man page for the full list with descriptions.

## SEE ALSO

[**curl\_easy\_getinfo**(3)](/curl_easy_getinfo/3.md), [**curl\_easy\_perform**(3)](/curl_easy_perform/3.md), [**curl\_easy\_setopt**(3)](/curl_easy_setopt/3.md), [**curl\_ws\_recv**(3)](/curl_ws_recv/3.md), [**libcurl-ws**(3)](/libcurl-ws/3.md)