CURLOPT_UPKEEP_INTERVAL_MS - connection upkeep interval

Added in curl 7.62.0

CURL_UPKEEP_INTERVAL_DEFAULT (currently defined as 60000L, which is 60 seconds)

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.

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); } }

CURLOPT_UPKEEP_INTERVAL_MS - connection upkeep interval

This functionality affects all supported protocols

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).

CURLOPT_TCP_KEEPALIVE(3) libcurl 2025-06-16 CURLOPT_UPKEEP_INTERVAL_MS(3)

#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPKEEP_INTERVAL_MS, long upkeep_interval_ms);