curl / libcurl / API / curl_easy_init

curl_ws_recv - receive websocket data

Name

curl_ws_recv - receive WebSocket data

Synopsis

#include <curl/curl.h>
 
CURLcode curl_ws_recv(CURL *curl, void *buffer, size_t buflen,
                      size_t *recv, const struct curl_ws_frame **meta);

Description

This function call is EXPERIMENTAL.

Retrieves as much as possible of a received WebSocket data fragment into the buffer, but not more than buflen bytes. recv is set to the number of bytes actually stored.

If there is more fragment data to deliver than what fits in the provided buffer, libcurl returns a full buffer and the application needs to call this function again to continue draining the buffer.

If the function call is successful, the meta pointer gets set to point to a const struct curl_ws_frame that contains information about the received data. That struct must not be freed and its contents must not be relied upon anymore once another WebSocket function is called. See the curl_ws_meta for details on that struct.a

Protocols

This functionality affects ws only

Example

int main(void)
{
  size_t rlen;
  const struct curl_ws_frame *meta;
  char buffer[256];
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res = curl_ws_recv(curl, buffer, sizeof(buffer), &rlen, &meta);
    if(res)
      printf("error: %s\n", curl_easy_strerror(res));
  }
}

Availability

Added in curl 7.86.0

Return value

Returns CURLE_OK if everything is okay, and a non-zero number for errors. Returns CURLE_GOT_NOTHING if the associated connection is closed.

Instead of blocking, the function returns CURLE_AGAIN. The correct behavior is then to wait for the socket to signal readability before calling this function again.