---
name: "CURLOPT_TCP_KEEPALIVE"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_TCP_KEEPALIVE"
---

# CURLOPT\_TCP\_KEEPALIVE(3)

TCP keep-alive probing

## NAME

CURLOPT\_TCP\_KEEPALIVE - TCP keep-alive probing

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TCP_KEEPALIVE, long probe);
```

## DESCRIPTION

Pass a long. If set to 1, TCP keepalive probes are used. The delay and frequency of these probes can be controlled by the *[CURLOPT\_TCP\_KEEPIDLE(3)](/CURLOPT_TCP_KEEPIDLE/3.md)*, *[CURLOPT\_TCP\_KEEPINTVL(3)](/CURLOPT_TCP_KEEPINTVL/3.md)*, and *[CURLOPT\_TCP\_KEEPCNT(3)](/CURLOPT_TCP_KEEPCNT/3.md)* options, provided the operating system supports them. Set to 0 (default behavior) to disable keepalive probes.

## DEFAULT

0

## PROTOCOLS

This functionality affects tcp only

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    /* enable TCP keep-alive for this transfer */
    curl_easy_setopt(curl, CURLOPT_TCP_KEEPALIVE, 1L);
    /* keep-alive idle time to 120 seconds */
    curl_easy_setopt(curl, CURLOPT_TCP_KEEPIDLE, 120L);
    /* interval time between keep-alive probes: 60 seconds */
    curl_easy_setopt(curl, CURLOPT_TCP_KEEPINTVL, 60L);
    /* maximum number of keep-alive probes: 3 */
    curl_easy_setopt(curl, CURLOPT_TCP_KEEPCNT, 3L);
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in curl 7.25.0

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_LOW\_SPEED\_LIMIT**(3)](/CURLOPT_LOW_SPEED_LIMIT/3.md), [**CURLOPT\_MAX\_RECV\_SPEED\_LARGE**(3)](/CURLOPT_MAX_RECV_SPEED_LARGE/3.md), [**CURLOPT\_TCP\_KEEPCNT**(3)](/CURLOPT_TCP_KEEPCNT/3.md), [**CURLOPT\_TCP\_KEEPIDLE**(3)](/CURLOPT_TCP_KEEPIDLE/3.md), [**CURLOPT\_TCP\_KEEPINTVL**(3)](/CURLOPT_TCP_KEEPINTVL/3.md)