curl / libcurl / API / curl_easy_setopt / CURLOPT_UPKEEP_INTERVAL_MS

CURLOPT_UPKEEP_INTERVAL_MS explained

Name

CURLOPT_UPKEEP_INTERVAL_MS - connection upkeep interval

Synopsis

#include <curl/curl.h>
 
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 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 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)

Protocols

This functionality affects all supported protocols

Example

int main(void)
{
  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 curl 7.62.0

Return value

Returns CURLE_OK