NAME

       curl_easy_upkeep - keep existing connections alive

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).

       If  you call this function on an easy handle that uses a shared connection cache then upkeep is performed
       on the connections in that cache, even if those connections were never used by the easy handle. (Added in
       8.10.0)

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

       This function returns a CURLcode indicating success or error.

       CURLE_OK (0) means everything was OK,  non-zero  means  an  error  occurred,  see  libcurl-errors(3).  If
       CURLOPT_ERRORBUFFER(3) was set with curl_easy_setopt(3) there can be an error message stored in the error
       buffer when non-zero is returned.

SEE ALSO

       CURLOPT_TCP_KEEPALIVE(3), CURLOPT_TCP_KEEPIDLE(3)

libcurl                                            2025-03-05                                curl_easy_upkeep(3)