NAME

curl_easy_upkeep - Perform any connection upkeep checks.

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_upkeep(CURL *handle);

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.

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.

This function must be explicitly called in order to perform the upkeep work. The connection upkeep interval is set with CURLOPT_UPKEEP_INTERVAL_MS(3).

AVAILABILITY

Added in 7.62.0.

RETURN VALUE

On success, returns CURLE_OK.

On failure, returns the appropriate error code.

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);
}