Getting Ip Address of Client

Get the client IP address using PHP

The simplest way to get the visitor’s/client’s IP address is using the $_SERVER['REMOTE_ADDR'] or $_SERVER['REMOTE_HOST'] variables.

However, sometimes this does not return the correct IP address of the visitor, so we can use some other server variables to get the IP address.

The below both functions are equivalent with the difference only in how and from where the values are retrieved.

getenv() is used to get the value of an environment variable in PHP.

// Function to get the client IP address
function get_client_ip() {
$ipaddress = '';
if (getenv('HTTP_CLIENT_IP'))
$ipaddress = getenv('HTTP_CLIENT_IP');
else if(getenv('HTTP_X_FORWARDED_FOR'))
$ipaddress = getenv('HTTP_X_FORWARDED_FOR');
else if(getenv('HTTP_X_FORWARDED'))
$ipaddress = getenv('HTTP_X_FORWARDED');
else if(getenv('HTTP_FORWARDED_FOR'))
$ipaddress = getenv('HTTP_FORWARDED_FOR');
else if(getenv('HTTP_FORWARDED'))
$ipaddress = getenv('HTTP_FORWARDED');
else if(getenv('REMOTE_ADDR'))
$ipaddress = getenv('REMOTE_ADDR');
else
$ipaddress = 'UNKNOWN';
return $ipaddress;
}

$_SERVER is an array that contains server variables created by the web server.

// Function to get the client IP address
function get_client_ip() {
$ipaddress = '';
if (isset($_SERVER['HTTP_CLIENT_IP']))
$ipaddress = $_SERVER['HTTP_CLIENT_IP'];
else if(isset($_SERVER['HTTP_X_FORWARDED_FOR']))
$ipaddress = $_SERVER['HTTP_X_FORWARDED_FOR'];
else if(isset($_SERVER['HTTP_X_FORWARDED']))
$ipaddress = $_SERVER['HTTP_X_FORWARDED'];
else if(isset($_SERVER['HTTP_FORWARDED_FOR']))
$ipaddress = $_SERVER['HTTP_FORWARDED_FOR'];
else if(isset($_SERVER['HTTP_FORWARDED']))
$ipaddress = $_SERVER['HTTP_FORWARDED'];
else if(isset($_SERVER['REMOTE_ADDR']))
$ipaddress = $_SERVER['REMOTE_ADDR'];
else
$ipaddress = 'UNKNOWN';
return $ipaddress;
}

Correct way of getting Client's IP Addresses from http.Request

Looking at http.Request you can find the following member variables:

// HTTP defines that header names are case-insensitive.
// The request parser implements this by canonicalizing the
// name, making the first character and any characters
// following a hyphen uppercase and the rest lowercase.
//
// For client requests certain headers are automatically
// added and may override values in Header.
//
// See the documentation for the Request.Write method.
Header Header

// RemoteAddr allows HTTP servers and other software to record
// the network address that sent the request, usually for
// logging. This field is not filled in by ReadRequest and
// has no defined format. The HTTP server in this package
// sets RemoteAddr to an "IP:port" address before invoking a
// handler.
// This field is ignored by the HTTP client.
RemoteAddr string

You can use RemoteAddr to get the remote client's IP address and port (the format is "IP:port"), which is the address of the original requestor or the last proxy (for example a load balancer which lives in front of your server).

This is all you have for sure.

Then you can investigate the headers, which are case-insensitive (per documentation above), meaning all of your examples will work and yield the same result:

req.Header.Get("X-Forwarded-For") // capitalisation
req.Header.Get("x-forwarded-for") // doesn't
req.Header.Get("X-FORWARDED-FOR") // matter

This is because internally http.Header.Get will normalise the key for you. (If you want to access header map directly, and not through Get, you would need to use http.CanonicalHeaderKey first.)

Finally, "X-Forwarded-For" is probably the field you want to take a look at in order to grab more information about client's IP. This greatly depends on the HTTP software used on the remote side though, as client can put anything in there if it wishes to. Also, note the expected format of this field is the comma+space separated list of IP addresses. You will need to parse it a little bit to get a single IP of your choice (probably the first one in the list), for example:

// Assuming format is as expected
ips := strings.Split("10.0.0.1, 10.0.0.2, 10.0.0.3", ", ")
for _, ip := range ips {
fmt.Println(ip)
}

will produce:

10.0.0.1
10.0.0.2
10.0.0.3

How to get a user's client IP address in ASP.NET?

As others have said you can't do what you are asking. If you describe the problem you are trying to solve maybe someone can help?

E.g.

  • are you trying to uniquely identify your users?
  • Could you use a cookie, or the session ID perhaps instead of the IP address?

Edit The address you see on the server shouldn't be the ISP's address, as you say that would be a huge range. The address for a home user on broadband will be the address at their router, so every device inside the house will appear on the outside to be the same, but the router uses NAT to ensure that traffic is routed to each device correctly. For users accessing from an office environment the address may well be the same for all users. Sites that use IP address for ID run the risk of getting it very wrong - the examples you give are good ones and they often fail. For example my office is in the UK, the breakout point (where I "appear" to be on the internet) is in another country where our main IT facility is, so from my office my IP address appears to be not in the UK. For this reason I can't access UK only web content, such as the BBC iPlayer). At any given time there would be hundreds, or even thousands, of people at my company who appear to be accessing the web from the same IP address.

When you are writing server code you can never be sure what the IP address you see is referring to. Some users like it this way. Some people deliberately use a proxy or VPN to further confound you.

When you say your machine address is different to the IP address shown on StackOverflow, how are you finding out your machine address? If you are just looking locally using ipconfig or something like that I would expect it to be different for the reasons I outlined above. If you want to double check what the outside world thinks have a look at whatismyipaddress.com/.

This Wikipedia link on NAT will provide you some background on this.

How to determine a user's IP address in node

In your request object there is a property called socket, which is a net.Socket object. The net.Socket object has a property remoteAddress, therefore you should be able to get the IP with this call:

request.socket.remoteAddress

(if your node version is below 13, use the deprecated now request.connection.remoteAddress)

EDIT

As @juand points out in the comments, the correct method to get the remote IP, if the server is behind a proxy, is request.headers['x-forwarded-for']

EDIT 2

When using express with Node.js:

If you set app.set('trust proxy', true), req.ip will return the real IP address even if behind proxy. Check the documentation for further information

Express.js: how to get remote client address

If you are running behind a proxy like NGiNX or what have you, only then you should check for 'x-forwarded-for':

var ip = req.headers['x-forwarded-for'] || req.socket.remoteAddress 

If the proxy isn't 'yours', I wouldn't trust the 'x-forwarded-for' header, because it can be spoofed.

How do I get client IP address in ASP.NET Core?

The API has been updated. Not sure when it changed but according to Damien Edwards in late December, you can now do this:

var remoteIpAddress = request.HttpContext.Connection.RemoteIpAddress;

How to get client IP address in Laravel 5+

Looking at the Laravel API:

Request::ip();

Internally, it uses the getClientIps method from the Symfony Request Object:

public function getClientIps()
{
$clientIps = array();
$ip = $this->server->get('REMOTE_ADDR');
if (!$this->isFromTrustedProxy()) {
return array($ip);
}
if (self::$trustedHeaders[self::HEADER_FORWARDED] && $this->headers->has(self::$trustedHeaders[self::HEADER_FORWARDED])) {
$forwardedHeader = $this->headers->get(self::$trustedHeaders[self::HEADER_FORWARDED]);
preg_match_all('{(for)=("?\[?)([a-z0-9\.:_\-/]*)}', $forwardedHeader, $matches);
$clientIps = $matches[3];
} elseif (self::$trustedHeaders[self::HEADER_CLIENT_IP] && $this->headers->has(self::$trustedHeaders[self::HEADER_CLIENT_IP])) {
$clientIps = array_map('trim', explode(',', $this->headers->get(self::$trustedHeaders[self::HEADER_CLIENT_IP])));
}
$clientIps[] = $ip; // Complete the IP chain with the IP the request actually came from
$ip = $clientIps[0]; // Fallback to this when the client IP falls into the range of trusted proxies
foreach ($clientIps as $key => $clientIp) {
// Remove port (unfortunately, it does happen)
if (preg_match('{((?:\d+\.){3}\d+)\:\d+}', $clientIp, $match)) {
$clientIps[$key] = $clientIp = $match[1];
}
if (IpUtils::checkIp($clientIp, self::$trustedProxies)) {
unset($clientIps[$key]);
}
}
// Now the IP chain contains only untrusted proxies and the client IP
return $clientIps ? array_reverse($clientIps) : array($ip);
}


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