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---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_UPKEEP_INTERVAL_MS
Section: 3
Source: libcurl
See-also:
- CURLOPT_TCP_KEEPALIVE (3)
Protocol:
- All
Added-in: 7.62.0
---
# NAME
CURLOPT_UPKEEP_INTERVAL_MS - connection upkeep interval
# SYNOPSIS
~~~c
#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%
# EXAMPLE
~~~c
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%
# RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
libcurl-errors(3).
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