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.TH CURLOPT_UPKEEP_INTERVAL_MS 3 "31 Oct 2018" libcurl libcurl
.SH NAME
CURLOPT_UPKEEP_INTERVAL_MS \- connection upkeep interval
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPKEEP_INTERVAL_MS,
                          long upkeep_interval_ms);
.fi
.SH 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 \fIcurl_easy_upkeep(3)\fP 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 \fIcurl_easy_upkeep(3)\fP
is called, an HTTP/2 PING frame is sent on the connection.

.SH DEFAULT
CURL_UPKEEP_INTERVAL_DEFAULT (currently defined as 60000L, which is 60 seconds)
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
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);
  }
}
.fi
.SH AVAILABILITY
Added in 7.62.0
.SH RETURN VALUE
Returns CURLE_OK
.SH SEE ALSO
.BR CURLOPT_TCP_KEEPALIVE "(3), "