---
name: "CURLOPT_LOCALPORT"
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_LOCALPORT"
---

# CURLOPT\_LOCALPORT(3)

local port number to use for socket

## NAME

CURLOPT\_LOCALPORT - local port number to use for socket

## SYNOPSIS

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

## 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)](/CURLOPT_INTERFACE/3.md)* and you are recommended to use *[CURLOPT\_LOCALPORTRANGE(3)](/CURLOPT_LOCALPORTRANGE/3.md)* as well when this option is set. Valid port numbers are 1 - 65535.

## DEFAULT

0, disabled - use whatever the system thinks is fine

## PROTOCOLS

This functionality affects all supported protocols

## 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

Added in curl 7.15.2

## 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

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