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                     23: .TH CURLOPT_UPKEEP_INTERVAL_MS 3 "31 Oct 2018" "libcurl 7.62.0" "curl_easy_setopt options"
                     24: .SH NAME
                     25: CURLOPT_UPKEEP_INTERVAL_MS \- connection upkeep interval
                     26: .SH SYNOPSIS
                     27: #include <curl/curl.h>
                     28: 
                     29: CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPKEEP_INTERVAL_MS, long upkeep_interval_ms);
                     30: .SH DESCRIPTION
                     31: Some protocols have "connection upkeep" mechanisms. These mechanisms usually
                     32: send some traffic on existing connections in order to keep them alive; this
                     33: can prevent connections from being closed due to overzealous firewalls, for
                     34: example.
                     35: 
                     36: The user needs to explicitly call \fIcurl_easy_upkeep(3)\fP in order to
                     37: perform the upkeep work.
                     38: 
                     39: Currently the only protocol with a connection upkeep mechanism is HTTP/2: when
                     40: the connection upkeep interval is exceeded and \fIcurl_easy_upkeep(3)\fP
                     41: is called, an HTTP/2 PING frame is sent on the connection.
                     42: 
                     43: .SH DEFAULT
                     44: CURL_UPKEEP_INTERVAL_DEFAULT (currently defined as 60000L, which is 60 seconds)
                     45: .SH EXAMPLE
                     46: .nf
                     47: CURL *curl = curl_easy_init();
                     48: if(curl) {
                     49:   /* Make a connection to an HTTP/2 server. */
                     50:   curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
                     51: 
                     52:   /* Set the interval to 30000ms / 30s */
                     53:   curl_easy_setopt(curl, CURLOPT_UPKEEP_INTERVAL_MS, 30000L);
                     54: 
                     55:   curl_easy_perform(curl);
                     56: 
                     57:   /* Perform more work here. */
                     58: 
                     59:   /* While the connection is being held open, curl_easy_upkeep() can be
                     60:      called. If curl_easy_upkeep() is called and the time since the last
                     61:      upkeep exceeds the interval, then an HTTP/2 PING is sent. */
                     62:   curl_easy_upkeep(curl);
                     63: 
                     64:   /* Perform more work here. */
                     65: 
                     66:   /* always cleanup */
                     67:   curl_easy_cleanup(curl);
                     68: }
                     69: .fi
                     70: .SH AVAILABILITY
                     71: Added in 7.62.0
                     72: .SH RETURN VALUE
                     73: Returns CURLE_OK