CURLOPT_UPKEEP_INTERVAL_MS

Section: curl_easy_setopt options (3)
Updated: November 04, 2020
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NAME

CURLOPT_UPKEEP_INTERVAL_MS - connection upkeep interval

SYNOPSIS

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPKEEP_INTERVAL_MS, long upkeep_interval_ms);

DESCRIPTION

Some protocols have "connection upkeep" mechanisms. These mechanisms usually send some traffic on existing connections in order to keep them alive; this can prevent connections from being closed due to overzealous firewalls, for example.

The user needs to explicitly call curl_easy_upkeep(3) in order to perform the upkeep work.

Currently the only protocol with a connection upkeep mechanism is HTTP/2: when the connection upkeep interval is exceeded and curl_easy_upkeep(3) is called, an HTTP/2 PING frame is sent on the connection.

DEFAULT

CURL_UPKEEP_INTERVAL_DEFAULT (currently defined as 60000L, which is 60 seconds)

EXAMPLE

CURL *curl = curl_easy_init();
if(curl) {
  /* Make a connection to an HTTP/2 server. */
  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

  /* Set the interval to 30000ms / 30s */
  curl_easy_setopt(curl, CURLOPT_UPKEEP_INTERVAL_MS, 30000L);

  curl_easy_perform(curl);

  /* Perform more work here. */

  /* While the connection is being held open, curl_easy_upkeep() can be
     called. If curl_easy_upkeep() is called and the time since the last
     upkeep exceeds the interval, then an HTTP/2 PING is sent. */
  curl_easy_upkeep(curl);

  /* Perform more work here. */

  /* always cleanup */
  curl_easy_cleanup(curl);
}

AVAILABILITY

Added in 7.62.0

RETURN VALUE

Returns CURLE_OK