curl / libcurl / API / curl_easy_send

curl_easy_send - sends raw data over a connection

Name

curl_easy_send - sends raw data over an "easy" connection

Synopsis

#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 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 option before calling curl_easy_perform or curl_multi_perform. Note that curl_easy_send 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 and the call should be retried later with the same buffer-content and a buflen no smaller than the original buflen. - 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 with CURLINFO_ACTIVESOCKET.

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

Protocols

This functionality affects all supported protocols

Example

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    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);
    result = curl_easy_perform(curl);
 
    if(result == CURLE_OK) {
      curl_socket_t sockfd;
      size_t sent;
      /* Extract the socket from the curl handle - we need it for waiting. */
      result = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
 
      /* send data */
      result = curl_easy_send(curl, "hello", 5, &sent);
    }
  }
}

Availability

Added in curl 7.18.2

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. The buffer passed to the retry call should hold the _same data_ as the original one and buflen should be _no smaller_ than before.

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