PHP | Get private IP address from a client user?

Question

I know question but didn't find real answer on stackoverflow. This is not X_FORWARDED_FOR, SERVER_NAME or SERVER_REMOTE_ADDR, I want get local IP address of remote client connected to my server to detect who is really on local remote network is connected.

Explain this:

ISP  <---->  ROUTER <----> LOCAL NETWORK <----> LOCAL PC

What I want to know?

1. Public IP address of connected remote client $_SERVER["REMOTE_ADDR"], okay, but!...
2. Local IP address of connected client on public network (192.168.x.x, 10.x.x.x, 172.x.x.x)

How to solve this problem? I have answer, so I think this should be know for everyone if want to know local IP address:

You should use CURL and curl_getinfo() function. Then, point URL address anyone that you want (your main server ip or whatever), for example:

<?php
    $ch = curl_init();

    $opt = curl_setopt($ch, CURLOPT_URL, "YOUR_SOME_URL_ADDRESS"); 

    curl_exec($ch);

    $response = curl_getinfo($ch);

    $result = array('client_public_address' => $response["primary_ip"],
                    'client_local_address' => $response["local_ip"]
            );

    var_dump($result);

    curl_close($ch);

?>

Focus on $response["primary_ip"] which responses your Public address and $response["local_ip"] which reponses local address. Now this is example:

ISP  <---->  ROUTER <----> LOCAL NETWORK <----> LOCAL PC
 /\                                              /\
 ||                                              ||
 \/                                              \/
$response["primary_ip"]                  <----> $response["local_ip"]
213.x.x.x  (for example)                        192.168.1.3 (for example)

Result:

array (size=2)
  'client_public_address' => string '213.xxx.xxx.xxx' (length=14)
  'client_local_address'  => string '192.168.1.3' (length=11)

This will NOT be giving a REAL local IP address!

Thank you.

Solution 1

This will never get to work.
First, you need an HTTP server on a client to make it response to CURL.
Even if ther would be - it is not guarantted to return whatever "local IP". Next, an HTTP server which pings it's clients back looks suspicious and most likely gets banned.

Anyway, I tried your code on a remote IP:

array(2) {
  ["client_public_address"]=>
  string(7) "8.8.8.8"
  ["client_local_address"]=>
  string(0) ""
}

it returned nothing

While when I tried my local router it works okay

array(2) {
  ["client_public_address"]=>
  string(13) "XXX"
  ["client_local_address"]=>
  string(12) "192.168.1.37"
}

It works only for your own local router, but it cannot get whatever local address from a remote system.
Frankly, it shows you just local IP address assigned to your PC.

Solution 2

The local IP addressed is not exposed to the application layer by default. You need lower level tools that can extract this information from the network packets.

Comments

[Marin Sagovac]

Yes. You are right. I have been tested on VPS server it will return NULL. My mistakes, sorry.

[Marin Sagovac]

This isn't for getting local IP address.