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54ded66618
- always assign the curl_easy_perform() return code (and declare the necessary 'result' variable for it) - always call curl_easy_cleanup() on the created easy handles Closes #21364
85 lines
2 KiB
Markdown
85 lines
2 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_UPKEEP_INTERVAL_MS
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_TCP_KEEPALIVE (3)
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Protocol:
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- All
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Added-in: 7.62.0
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---
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# NAME
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CURLOPT_UPKEEP_INTERVAL_MS - connection upkeep interval
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPKEEP_INTERVAL_MS,
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long upkeep_interval_ms);
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~~~
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# DESCRIPTION
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Some protocols have "connection upkeep" mechanisms. These mechanisms usually
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send some traffic on existing connections in order to keep them alive; this
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can prevent connections from being closed due to overzealous firewalls, for
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example.
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The user needs to explicitly call curl_easy_upkeep(3) in order to
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perform the upkeep work.
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Currently the only protocol with a connection upkeep mechanism is HTTP/2: when
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the connection upkeep interval is exceeded and curl_easy_upkeep(3)
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is called, an HTTP/2 PING frame is sent on the connection.
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# DEFAULT
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CURL_UPKEEP_INTERVAL_DEFAULT (currently defined as 60000L, which is 60 seconds)
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# %PROTOCOLS%
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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CURLcode result;
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/* Make a connection to an HTTP/2 server. */
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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/* Set the interval to 30000ms / 30s */
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curl_easy_setopt(curl, CURLOPT_UPKEEP_INTERVAL_MS, 30000L);
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result = curl_easy_perform(curl);
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/* Perform more work here. */
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/* While the connection is being held open, curl_easy_upkeep() can be
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called. If curl_easy_upkeep() is called and the time since the last
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upkeep exceeds the interval, then an HTTP/2 PING is sent. */
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curl_easy_upkeep(curl);
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/* Perform more work here. */
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/* always cleanup */
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curl_easy_cleanup(curl);
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}
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}
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~~~
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# %AVAILABILITY%
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# RETURN VALUE
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curl_easy_setopt(3) returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
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libcurl-errors(3).
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