curl_easy_upkeep(3) Library Functions Manual curl_easy_upkeep(3)
NAME
curl_easy_upkeep - keep existing connections alive
SYNOPSIS
#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 in-
terval 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 pre-
vent 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_INTER-
VAL_MS(3).
If you call this function on an easy handle that uses a shared connec-
tion 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
This functionality affects all supported protocols
EXAMPLE
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
Added in curl 7.62.0
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.
SEE ALSO
CURLOPT_TCP_KEEPALIVE(3), CURLOPT_TCP_KEEPIDLE(3)
libcurl 2026-07-12 curl_easy_upkeep(3)
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