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 will take care of proxy negotiation and
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.
To establish the connection, set CURLOPT_CONNECT_ONLY option before
calling curl_easy_perform(3). Note that curl_easy_send(3) will not
work on connections that were created without this option.
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.
Added in 7.18.2.
On 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.
See sendrecv.c in docs/examples directory for usage example.