curl / libcurl / API / curl_multi_setopt / CURLMOPT_PIPELINING

CURLMOPT_PIPELINING explained

Name

CURLMOPT_PIPELINING - enable HTTP multiplexing

#include <curl/curl.h>
 
CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PIPELINING, long bitmask);

Pass in the correct value in the bitmask parameter to instruct libcurl to enable multiplexing for this multi handle.

With multiplexing enabled, libcurl attempts to do multiple transfers over the same connection when doing parallel transfers to the same hosts.

CURLPIPE_NOTHING (0)

Make no attempts at multiplexing.

CURLPIPE_HTTP1 (1)

This bit is deprecated and has no effect since version 7.62.0.

CURLPIPE_MULTIPLEX (2)

If this bit is set, libcurl tries to multiplex the new transfer over an existing connection if possible. This requires HTTP/2 or HTTP/3.

This functionality affects http only

int main(void)
{
  CURLM *m = curl_multi_init();
  /* try HTTP/2 multiplexing */
  curl_multi_setopt(m, CURLMOPT_PIPELINING, CURLPIPE_MULTIPLEX);
}

The multiplex support bit was added in 7.43.0. HTTP/1 Pipelining support was disabled in 7.62.0.

Since 7.62.0, CURLPIPE_MULTIPLEX is enabled by default.

Before that, default was CURLPIPE_NOTHING.

Added in curl 7.16.0

curl_multi_setopt returns a CURLMcode indicating success or error.

CURLM_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors.