curl_easy_recv - receives raw data on an "easy" connection
#include <curl/easy.h>
CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n);
This function receives raw data from the established connection. You may use it
together with
curl_easy_send(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 setup.
buffer is a pointer to your buffer that will get the received data.
buflen is the maximum amount of data you can get in that buffer. The
variable
n points to will receive the number of received bytes.
To establish the connection, set
CURLOPT_CONNECT_ONLY(3) option before
calling
curl_easy_perform(3) or
curl_multi_perform(3). Note that
does not work on connections that were created
without this option.
The call will return
CURLE_AGAIN if there is no data to read - the socket
is used in non-blocking mode internally. When
CURLE_AGAIN is returned,
use your operating system facilities like
select(2) to wait for data.
The socket may be obtained using
curl_easy_getinfo(3) with
CURLINFO_ACTIVESOCKET(3).
Wait on the socket only if returns
CURLE_AGAIN.
The reason for this is libcurl or the SSL library may internally cache some
data, therefore you should call until all data is
read which would include any cached data.
Furthermore if you wait on the socket and it tells you there is data to read,
may return
CURLE_AGAIN if the only data that
was read was for internal SSL processing, and no other data is available.
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) {
/* Extract the socket from the curl handle -
we will need it for waiting. */
res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
/* read data */
res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
}
Added in 7.18.2.
On success, returns
CURLE_OK, stores the received data into
buffer, and the number of bytes it actually read into
*n.
On failure, returns the appropriate error code.
The function may return
CURLE_AGAIN. In this case, use your operating
system facilities to wait until data can be read, and retry.
Reading exactly 0 bytes indicates a closed connection.
If there's no socket available to use from the previous transfer, this function
returns
CURLE_UNSUPPORTED_PROTOCOL.
curl_easy_setopt(3),
curl_easy_perform(3),
curl_easy_getinfo(3),
curl_easy_send(3)