curl_easy_send (3) - Linux Man Pages
curl_easy_send: sends raw data over an "easy" connection
NAMEcurl_easy_send - sends raw data over an "easy" connection
DESCRIPTIONThis 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 will take care of proxy negotiation and connection set-up.
buffer is a pointer to the data of length buflen that you want sent. The variable n points to will receive the number of sent bytes.
You must ensure that the socket is writable before calling curl_easy_send(3), otherwise the call will return CURLE_AGAIN - the socket is used in non-blocking mode internally. Use curl_easy_getinfo(3) with CURLINFO_LASTSOCKET to obtain the socket; use your operating system facilities like select(2) to check if it can be written to.
AVAILABILITYAdded in 7.18.2.
RETURN VALUEOn success, returns CURLE_OK and stores the number of bytes actually sent into *n. Note that this may very well be less than the amount you wanted to send.
On failure, returns the appropriate error code.