1---
2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
3SPDX-License-Identifier: curl
4Title: CURLOPT_UPKEEP_INTERVAL_MS
5Section: 3
6Source: libcurl
7See-also:
8  - CURLOPT_TCP_KEEPALIVE (3)
9Protocol:
10  - All
11---
12
13# NAME
14
15CURLOPT_UPKEEP_INTERVAL_MS - connection upkeep interval
16
17# SYNOPSIS
18
19~~~c
20#include <curl/curl.h>
21
22CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPKEEP_INTERVAL_MS,
23                          long upkeep_interval_ms);
24~~~
25
26# DESCRIPTION
27
28Some protocols have "connection upkeep" mechanisms. These mechanisms usually
29send some traffic on existing connections in order to keep them alive; this
30can prevent connections from being closed due to overzealous firewalls, for
31example.
32
33The user needs to explicitly call curl_easy_upkeep(3) in order to
34perform the upkeep work.
35
36Currently the only protocol with a connection upkeep mechanism is HTTP/2: when
37the connection upkeep interval is exceeded and curl_easy_upkeep(3)
38is called, an HTTP/2 PING frame is sent on the connection.
39
40# DEFAULT
41
42CURL_UPKEEP_INTERVAL_DEFAULT (currently defined as 60000L, which is 60 seconds)
43
44# EXAMPLE
45
46~~~c
47int main(void)
48{
49  CURL *curl = curl_easy_init();
50  if(curl) {
51    /* Make a connection to an HTTP/2 server. */
52    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
53
54    /* Set the interval to 30000ms / 30s */
55    curl_easy_setopt(curl, CURLOPT_UPKEEP_INTERVAL_MS, 30000L);
56
57    curl_easy_perform(curl);
58
59    /* Perform more work here. */
60
61    /* While the connection is being held open, curl_easy_upkeep() can be
62       called. If curl_easy_upkeep() is called and the time since the last
63       upkeep exceeds the interval, then an HTTP/2 PING is sent. */
64    curl_easy_upkeep(curl);
65
66    /* Perform more work here. */
67
68    /* always cleanup */
69    curl_easy_cleanup(curl);
70  }
71}
72~~~
73
74# AVAILABILITY
75
76Added in 7.62.0
77
78# RETURN VALUE
79
80Returns CURLE_OK
81