curl/docs/libcurl/opts/CURLOPT_LOCALPORTRANGE.md
Daniel Stenberg e694c8284a
docs/libcurl/opts: clarify the return values
Expand a little.

- mention the type name of the return code
- avoid stating which exact return codes that might be returned, as that
  varies over time, builds and conditions
- avoid stating some always return OK
- refer to the manpage documenting all the return codes

Closes #15900
2025-01-02 17:13:33 +01:00

69 lines
1.5 KiB
Markdown

---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_LOCALPORTRANGE
Section: 3
Source: libcurl
See-also:
- CURLOPT_INTERFACE (3)
- CURLOPT_LOCALPORT (3)
Protocol:
- All
Added-in: 7.15.2
---
# NAME
CURLOPT_LOCALPORTRANGE - number of additional local ports to try
# SYNOPSIS
~~~c
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_LOCALPORTRANGE,
long range);
~~~
# DESCRIPTION
Pass a long. The *range* argument is the number of attempts libcurl makes
to find a working local port number. It starts with the given
CURLOPT_LOCALPORT(3) and adds one to the number for each retry. Setting
this option to 1 or below makes libcurl only do one try for the exact port
number. Port numbers by nature are scarce resources that are busy at times so
setting this value to something too low might cause unnecessary connection
setup failures.
# DEFAULT
1
# %PROTOCOLS%
# EXAMPLE
~~~c
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
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);
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
~~~
# %AVAILABILITY%
# RETURN VALUE
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).