xref: /aosp_15_r20/external/curl/docs/libcurl/curl_easy_send.md (revision 6236dae45794135f37c4eb022389c904c8b0090d)

---
c: Copyright (C) Daniel Stenberg, <[email protected]>, et al.
SPDX-License-Identifier: curl
Title: curl_easy_send
Section: 3
Source: libcurl
See-also:
  - curl_easy_getinfo (3)
  - curl_easy_perform (3)
  - curl_easy_recv (3)
  - curl_easy_setopt (3)
Protocol:
  - All
Added-in: 7.18.2
---

# NAME

curl_easy_send - sends raw data over an "easy" connection

# SYNOPSIS

~~~c
#include <curl/curl.h>

CURLcode curl_easy_send(CURL *curl, const void *buffer,
                        size_t buflen, size_t *n);
~~~

# DESCRIPTION

This function sends arbitrary data over the established connection. You may
use it together with curl_easy_recv(3) to implement custom protocols
using libcurl. This functionality can be particularly useful if you use
proxies and/or SSL encryption: libcurl takes care of proxy negotiation and
connection setup.

**buffer** is a pointer to the data of length **buflen** that you want
sent. The variable **n** points to receives the number of sent bytes.

To establish the connection, set CURLOPT_CONNECT_ONLY(3) option before
calling curl_easy_perform(3) or curl_multi_perform(3). Note that
curl_easy_send(3) does not work on connections that were created without
this option.

The call returns **CURLE_AGAIN** if it is not possible to send data right now
- the socket is used in non-blocking mode internally. When **CURLE_AGAIN**
is returned, use your operating system facilities like *select(2)* to wait
until the socket is writable. The socket may be obtained using
curl_easy_getinfo(3) with CURLINFO_ACTIVESOCKET(3).

Furthermore if you wait on the socket and it tells you it is writable,
curl_easy_send(3) may return **CURLE_AGAIN** if the only data that was sent
was for internal SSL processing, and no other data could be sent.

# %PROTOCOLS%

# EXAMPLE

~~~c
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    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) {
      long sockfd;
      size_t sent;
      /* Extract the socket from the curl handle - we need it for waiting. */
      res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);

      /* send data */
      res = curl_easy_send(curl, "hello", 5, &sent);
    }
  }
}
~~~

# %AVAILABILITY%

# RETURN VALUE

On success, returns **CURLE_OK** and stores the number of bytes actually
sent into ***n**. Note that this may be less than the amount you wanted to
send.

On failure, returns the appropriate error code.

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

If there is no socket available to use from the previous transfer, this function
returns **CURLE_UNSUPPORTED_PROTOCOL**.