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(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)

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

SEE ALSO

       CURLOPT_TCP_KEEPALIVE(3)