curl/docs/libcurl/curl_easy_upkeep.3

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.TH curl_easy_upkeep 3 "31 Oct 2018" "libcurl 7.62.0" "libcurl Manual"
.SH NAME
curl_easy_upkeep - Perform any connection upkeep checks.
.SH SYNOPSIS
.B #include <curl/curl.h>

.BI "CURLcode curl_easy_upkeep(CURL *" handle ");"
.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.

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.

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

.SH AVAILABILITY
Added in 7.62.0.
.SH RETURN VALUE
On success, returns \fBCURLE_OK\fP.

On failure, returns the appropriate error code.

.SH EXAMPLE
.nf
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