CURLOPT\_TCP\_KEEPALIVE(3) Library Functions Manual CURLOPT\_TCP\_KEEPALIVE(3)

# [NAME](#NAME)

CURLOPT\_TCP\_KEEPALIVE - TCP keep-alive probing

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#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)*](/man/os/curl/CURLOPT_TCP_KEEPIDLE.3), [*CURLOPT\_TCP\_KEEPINTVL(3)*](/man/os/curl/CURLOPT_TCP_KEEPINTVL.3), and [*CURLOPT\_TCP\_KEEPCNT(3)*](/man/os/curl/CURLOPT_TCP_KEEPCNT.3) options, provided the operating system supports them. Set to 0 (default behavior) to disable keepalive probes.

# [DEFAULT](#DEFAULT)

0

# [PROTOCOLS](#PROTOCOLS)

This functionality affects tcp only

# [EXAMPLE](#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](#AVAILABILITY)

Added in curl 7.25.0

# [RETURN VALUE](#RETURN_VALUE)

[*curl\_easy\_setopt(3)*](/man/os/curl/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)*](/man/os/curl/libcurl-errors.3).

# [SEE ALSO](#SEE_ALSO)

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

2026-10-01 libcurl

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Document: CURLOPT_TCP_KEEPALIVE(3) from curl 8.22.0-r4 (Chainguard OS)
Source: https://github.com/curl/curl.git