CURLINFO_PRIMARY_PORT(3)

💅 CURLINFO_PRIMARY_PORT(3) — like, the manual page, bestie

okay so real talk, this is one of those libcurl manual pages (that's the Library Functions Manual vibe, iykyk) and honestly? it's a little cutie. Let's get into it ✨

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🌸 NAME 🌸

CURLINFO_PRIMARY_PORT — last destination port number

✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_PRIMARY_PORT, long *portp);

🎀 DESCRIPTION 🎀

okay so what you're doing here is passing a pointer to a long and it receives the destination port of the most recent connection done with this curl handle. that's it, that's the whole vibe 💅

and it's specifically the destination port of the actual TCP or UDP connection that libcurl used. so like, important nuance incoming:

• if a proxy was used for the most recent transfer → this is the port number of the proxy
• if no proxy was used → this is the port number of the most recently accessed URL

if the connection was done using QUIC, the port number is a UDP port number. (not me double-checking which port family we're in 🫶)

and if no connection was established, or if the protocol doesn't even use ports? then -1 is returned. no cap, that's your "nope" signal 😭

🦋 PROTOCOLS 🦋

This functionality affects all supported protocols — every single one, periodt 👑

🌈 EXAMPLE 🌈

okay here's the actual code, copy it exactly bestie, don't be creative with it:

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    result = curl_easy_perform(curl);
    if(result == CURLE_OK) {
      long port;
      result = curl_easy_getinfo(curl, CURLINFO_PRIMARY_PORT, &port);
      if(!result)
        printf("Connected to remote port: %ld\n", port);
    }
    curl_easy_cleanup(curl);
  }
}

⭐ AVAILABILITY ⭐

Added in curl 7.21.0 — so your fave has been iconic for a minute 🕰️

💖 RETURN VALUE 💖

curl_easy_getinfo(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) for the deets

💜 SEE ALSO 💜

• CURLINFO_LOCAL_PORT(3)
• CURLINFO_PRIMARY_IP(3)
• curl_easy_getinfo(3)
• curl_easy_setopt(3)

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ngl, this page is short and sweet and I'm obsessed. go forth and check your ports, bestie 🌸

libcurl manual, dated 2026-10-12 — that's the source/version and date, mwah, signing off 🫶✨