🦉Server-to-Server (S2S) Callback Configuration

Server-to-Server callbacks allow you to receive reward confirmation events directly from the offerwall via HTTP requests.

Go to the Offerwall section, open the Overview tab, select your app from the list, then click the S2S Callbacks card in your app’s dashboard to create or manage S2S callbacks. Click Configure to get started.

1. Setup Callback URL

When a user completes an offer and earns a reward, an HTTP GET request is sent to your configured callback URL. The request includes a set of query parameters that convey key reward information.

1.1. Base URL

You must first define your Base URL — the endpoint on your server that will handle the incoming callback.

BaseUrl and Final Callback Url

For any custom URL requirements or special customizations, please contact your Account Manager.

1.2. Parameter Configuration

Parameters can be added using a key-value builder interface:

• Keys are fully editable.

• Values are selected from predefined macros (e.g., user_id, value, etc.) via a searchable dropdown.

• Static parameters can also be added with hardcoded values.

• Some default system parameters are pre-filled (e.g., user_id, value, token, signature) and appear in the list with locked values.

Callback Macros Key Values

Example callback setup:

Callback URL set by you: http://www.example.com/payments/offers/pubscale

Request sent from us: HTTP GET http://www.example.com/payments/offers/pubscale?user_id={user_id}&value={value}&token={token}&signature={signature}

Query Params	Description
user_id *	The 'unique_id' set while initializing the SDK.
value *	The decimal value of the reward earned by the user.
token *	A token that uniquely represents the transaction.
signature *	Hash of the above values to verify the request (more info below).
click_datetime	The Unix timestamp of when the user clicked the offer. Eg1718509200
conversion_datetime	The Unix timestamp of when the user completed the offer. Eg 1718509400
country	The user's country in ISO 3166-1 alpha-2 code. Example: IN, US
gaid	The user's Google Advertising ID (Android only). Example: a1b2c3d4-e5f6-7890-gh12-ijkl3456mnop
goal_name	The name assigned to the reward or task. Example: Complete 5th Level
goal_value	A unique code for the completed task. Example: FB_Level_Complete_5
idfa	Apple’s Identifier for Advertisers (iOS only). Example: 6D92078A-8246-4BA4-AE5B-76104861E7DC
ip	The IP address of the user when the offer was clicked. Example: 192.168.0.101
offer_id	A unique identifier for the completed offer. Example: 45678
offer_name	The title of the completed offer. Example: Tappy Plane - GameApp
package_name	The package name of the app associated with the offer. Example: com.tappyplane.gameapp
payout_usd	The payout amount in USD for the completed offer. Example: 0.75
useragent	The user’s browser and device information string. Example: Mozilla/5.0 (Linux; Android 10; Pixel 3)

_{1.3. Server Response}

Responding to the callback URL with status codes between and including the values 200 to 299 will mark the callback as successfully delivered.

In the event of the server not responding with any of the aforementioned status codes, the request will be retried 6 times at different intervals. You can utilize the unique token sent in the request to avoid rewarding the user multiple times for the same callback.

1.4. Hash validation

The value sent in the signature parameter can be used to validate the identity of the origin of the request. The value is an MD5 hash of the template below. The secret key is an additional key that will be provided along with the APP API KEY.

PHP

function calculateHash() {
	
	$user = $_GET['user_id'];
	$token = $_GET['token'];
	$value = $_GET['value'];

	$template = <secret_key>. "." . $user . "." . (int)$value . "." $token;

	return calculateMD5($template);
}

function calculateMD5($data) {
	return hash('md5', $data);
}

$hash = $_GET['signature'];

if ($hash != calculateHash()) {
	return false
}

NodeJs

const md5 = require('md5')
  
const template = `${<secret_key>}.${<user_id>}.${Math.trunc(<value>)}.${<token>}`
const hash = md5(template)

if(signature != hash) {
    return false
}

Python

import hashlib

template = '{secret_key}.{user_id}.{value}.{token}'.format(secret_key=<secret_key>,user_id=<user_id>,value=int(<value>),token=<token>)
hash = hashlib.md5(template.encode('utf-8')).hexdigest()

if hash != <signature>:
    return false            

Golang

template := fmt.Sprintf("%s.%s.%d.%s", <secret_key>, <user_id>, <int({value>), <token>)
hash := toMD5(template)

  if hash != {signature} {
        return errors.New("invalid signature")
  }

func toMD5(text string) string {
  algorithm := md5.New()
  algorithm.Write([]byte(text))
  return hex.EncodeToString(algorithm.Sum(nil))
}

Example

secret_key = fa072672-d432-11c4-885a-EB1CdEc4Bb13 user_id = 30356439-8d15-4f47-B133-010a37C19eBD value = 100.1234 token = 525a5B8e-512b-441A-a10B-72d218c370e5

Final format = fa072672-d432-11c4-885a-EB1CdEc4Bb13.30356439-8d15-4f47-B133-010a37C19eBD.100.525a5B8e-512b-441A-a10B-72d218c370e5

Steps to validate the value of the hash

1. Concatenate the values in the above format.

2. Make sure to convert the value parameter from decimal to integer.

3. Calculate the MD5 hash of the concatenated value.

4. Build Hex encode of the generated value.

5. Verify if the calculated value is equal to the value sent in the signature parameter.

As the value of the secret key will only be known to you and PubScale’s server, the hash cannot be generated by a fraudulent third party.

1.5. IP Whitelisting

You can restrict the callbacks to be accepted only from our sever IP address(es). Please whitelist the following IP(s) and regularly check back to find possible changes

34.100.236.68

//Last updated at: Jan 23, 2024

2. Test Callback Tool

A dedicated modal tool is available to test your callback configuration before going live.

• Safely edit and test the callback URL without impacting your saved configuration.

• Input Fields:

  • User ID: Used to simulate a user session.

  • Custom Reward Value: Used to simulate a reward payout.

• This allows for quick verification of your endpoint and debugging of parameters.

The User ID you enter here must be the same as the User ID used in your SDK initialization