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---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: curl_easy_upkeep
Section: 3
Source: libcurl
See-also:
- CURLOPT_TCP_KEEPALIVE (3)
- CURLOPT_TCP_KEEPIDLE (3)
Protocol:
- All
Added-in: 7.62.0
---
# NAME
curl_easy_upkeep - keep existing connections alive
# SYNOPSIS
~~~c
#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.
For HTTP/2 we have an upkeep mechanism: when
the connection upkeep interval is exceeded and curl_easy_upkeep(3)
is called, an HTTP/2 PING frame is sent on the connection.
For MQTT the upkeep interval defines when to send ping requests to prevent the
server from disconnecting.
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%
# 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
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.
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