73 lines
2.3 KiB
Groff
73 lines
2.3 KiB
Groff
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.\" generated by cd2nroff 0.1 from curl_easy_upkeep.md
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.TH curl_easy_upkeep 3 "2025-07-07" libcurl
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.SH NAME
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curl_easy_upkeep \- keep existing connections alive
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLcode curl_easy_upkeep(CURL *handle);
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.fi
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.SH 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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For HTTP/2 we have an upkeep mechanism: when
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the connection upkeep interval is exceeded and \fIcurl_easy_upkeep(3)\fP
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is called, an HTTP/2 PING frame is sent on the connection.
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For MQTT the upkeep interval defines when to send ping requests to prevent the
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server from disconnecting.
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This function must be explicitly called in order to perform the upkeep work.
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The connection upkeep interval is set with
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\fICURLOPT_UPKEEP_INTERVAL_MS(3)\fP.
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If you call this function on an easy handle that uses a shared connection cache
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then upkeep is performed on the connections in that cache, even if those
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connections were never used by the easy handle. (Added in 8.10.0)
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.SH PROTOCOLS
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This functionality affects all supported protocols
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.SH EXAMPLE
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.nf
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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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/* 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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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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.fi
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.SH AVAILABILITY
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Added in curl 7.62.0
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.SH RETURN VALUE
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This function 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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\fIlibcurl\-errors(3)\fP. If \fICURLOPT_ERRORBUFFER(3)\fP was set with \fIcurl_easy_setopt(3)\fP
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there can be an error message stored in the error buffer when non\-zero is
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returned.
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.SH SEE ALSO
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.BR CURLOPT_TCP_KEEPALIVE (3),
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.BR CURLOPT_TCP_KEEPIDLE (3)
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