CURLOPT\_LOCALPORT(3) Library Functions Manual CURLOPT\_LOCALPORT(3)

# [NAME](#NAME)

CURLOPT\_LOCALPORT - local port number to use for socket

# [SYNOPSIS](#SYNOPSIS)

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

# [DESCRIPTION](#DESCRIPTION)

Pass a long. This sets the local port number of the socket used for the connection. This can be used in combination with [*CURLOPT\_INTERFACE(3)*](/man/os/curl/CURLOPT_INTERFACE.3) and you are recommended to use [*CURLOPT\_LOCALPORTRANGE(3)*](/man/os/curl/CURLOPT_LOCALPORTRANGE.3) as well when this option is set. Valid port numbers are 1 - 65535.

# [DEFAULT](#DEFAULT)

0, disabled - use whatever the system thinks is fine

# [PROTOCOLS](#PROTOCOLS)

This functionality affects all supported protocols

# [EXAMPLE](#EXAMPLE)

```
int main(void)
{


  CURL *curl = curl_easy_init();


  if(curl) {


    CURLcode result;


    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");


    curl_easy_setopt(curl, CURLOPT_LOCALPORT, 49152L);


    /* and try 20 more ports following that */


    curl_easy_setopt(curl, CURLOPT_LOCALPORTRANGE, 20L);


    result = curl_easy_perform(curl);


    curl_easy_cleanup(curl);


  }
}
```

# [AVAILABILITY](#AVAILABILITY)

Added in curl 7.15.2

# [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)

[**CURLINFO\_LOCAL\_PORT**(3)](/man/os/curl/CURLINFO_LOCAL_PORT.3), [**CURLOPT\_INTERFACE**(3)](/man/os/curl/CURLOPT_INTERFACE.3), [**CURLOPT\_LOCALPORTRANGE**(3)](/man/os/curl/CURLOPT_LOCALPORTRANGE.3)

2026-10-19 libcurl

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Document: CURLOPT_LOCALPORT(3) from curl 8.23.0-r1 (Chainguard OS)
Source: https://github.com/curl/curl.git