oracular (3) curl_easy_recv.3.gz

NAME

       curl_easy_recv - receives raw data on an "easy" connection

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n);

DESCRIPTION

       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 takes care of proxy negotiation and connection
       setup.

       buffer is a pointer to your buffer memory that gets populated by the received data. buflen is the maximum
       amount  of  data  you  can  get  in that buffer. The variable n points to receives 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 curl_easy_recv(3) does not work on connections that were created without
       this option.

       The call returns 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 curl_easy_recv(3) returns CURLE_AGAIN.  The reason for this is libcurl or  the
       SSL library may internally cache some data, therefore you should call curl_easy_recv(3) 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,  curl_easy_recv(3)  may
       return  CURLE_AGAIN  if the only data that was read was for internal SSL processing, and no other data is
       available.

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       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) {
             char buf[256];
             size_t nread;
             long sockfd;

             /* Extract the socket from the curl handle - we need it for waiting. */
             res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);

             /* read data */
             res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
           }
         }
       }

AVAILABILITY

       Added in curl 7.18.2

RETURN VALUE

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

SEE ALSO

       curl_easy_getinfo(3), curl_easy_perform(3), curl_easy_send(3), curl_easy_setopt(3)