Android Push Notification using Google Cloud Messaging (GCM) Part 1

Google Cloud Messaging enables android application to easily communicate with server for sending and receiving the data. Every time when new data is available to server it will deliver it to application in device as soon as device is found online.

We will cover push notification in two parts.

1. Registering with Google API Console and WebServer Configuration

2. Developing GCM supported Android Application

[su_note note_color=”#e6f7f3″ radius=”5″]Overview of GCM Communication between Client and Server

1. Android device sends SENDER_ID and APPLICATION_ID to GCM server for registration.

2. After registration success, GCM server issues a REGISTRATION_ID to android device

3. On receiving REGISTRATION_ID, android device will send this id to web server.

4. Web Server will store GCM registration id in it database for later usage.

5. Whenever a push notification is required to send, web server sends a message to GCM server along with registration id.

6. GCM server will deliver this message to android device using registration id. [/su_note]

Registration with Google APIs console

1. For enabling GCM support in an android application, We need to obtain api key from Google APIs Console page.   Login using your Google id, you will get option to create a new project. 




2. After creating project in above step, you will be redirected to new project. Note down project number here for later use. We will use this id as SENDER_ID in our android application. You can check it later on in project overview and project id and project number can be retrieved.




3. In API Project -> APIs & Auth section find Google Cloud Messaging for Android. Accept terms and conditions and toggle it’s status to ON.




4. After enabling GCM for Android, Go to APIs & auth -> Credentials and click create new key and select server key to generate API KEY.




In details, fill your allowed IP’s or just mention to allow all.



If you have completed above steps, you managed to get

1. Project Number


Configuring Web Server

[su_button url=”” target=”blank” style=”soft” background=”#51d461″ color=”#ffffff” size=”6″ center=”yes” icon=”icon: arrow-circle-o-down”]Download Complete Source Code[/su_button]


1. Download and install WampServer if not already installed. Run WampServer, click and start phpMyAdmin or navigate to http://localhost/phpmyadmin

2. Create a new database named gcm_demo. Navigate to SQL query run console and execute below query to create table users.

 `gcm_regid` text,

3. For sending POST request to GCM server, we will use PHP Client URL Library. Click wamp system tray icon and navigate to PHP -> PHP extensions and check if php_curl is enabled or not. If not, enable it.

4. Open www directory. Navigate wamp system tray icon -> www directory. Create a new directory name web_server_demo_gcm

5. Create a file named config.php. It will have info about database configuration and Google API KEY.

 * DB config
define("DB_HOST", "localhost");
define("DB_USER", "root");
define("DB_PASSWORD", "");
define("DB_DATABASE", "gcm_demo");

 * Google API Key
define("GOOGLE_API_KEY", "AIzaSyD1LdXienHG1o-fF-J-vnsJuYU159eRi5I");

6. Create another php file named db_connect.php for creating and closing database connection. Please refer php mysql functions for better understanding.

class DB_Connect {

    function __construct() {

    function __destruct() {

    //create database conn
    public function connect() {
        require_once 'config.php';

        $conn = mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);

        return $conn;

    // close database conn
    public function close() {


7. Create another file db_functions.php for performing mysql operations of adding and listing users.

class DB_Functions {

    private $db;

    function __construct() {
        include_once './db_connect.php';
        // connect to database
        $this->db = new DB_Connect();

    function __destruct() {

     * Store user and returning user details
    public function storeUser($gcm_regid) {
        // insert user into database
        $result = mysql_query("INSERT INTO reg_users(gcm_regid, created_at) VALUES('$gcm_regid', NOW())");
        // check for successful store
        if ($result) {
            // get user details
            $id = mysql_insert_id(); // last inserted id
            $result = mysql_query("SELECT * FROM reg_users WHERE id = $id") or die(mysql_error());
            // return user details
            if (mysql_num_rows($result) > 0) {
                return mysql_fetch_array($result);
            } else {
                return false;
        } else {
            return false;

     * list all users
    public function getAllUsers() {
        $result = mysql_query("select * FROM reg_users");
        return $result;


8. For sending push notification request to GCM server, create another file named gcm_sendmsg.php

class GCM_SendMsg {

    function __construct() {

     * send push notification
    public function send_notification($registatoin_ids, $message) {

        include_once './config.php';

        // Set POST request variable
        $url = '';

        $fields = array(
            'registration_ids' => $registatoin_ids,
            'data' => $message,

        $headers = array(
            'Authorization: key=' . GOOGLE_API_KEY,
            'Content-Type: application/json'
        // Open connection
        $ch = curl_init();

        // Set the url, number of POST vars, POST data
        curl_setopt($ch, CURLOPT_URL, $url);

        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

        // disable SSL certificate support
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));

        // execute post
        $result = curl_exec($ch);
        if ($result === FALSE) {
            die('Curl failed: ' . curl_error($ch));

        // Close connection
        echo $result;



9. Create yet another file register_user.php for saving user registration request from android device.

// response json
$json = array();

 * Registering a user device
 * Store reg id in users table
if (isset($_POST["regId"])) {
    $gcm_regid = $_POST["regId"]; 

    include_once './db_functions.php';
    include_once './gcm_sendmsg.php';

    $db = new DB_Functions();
    $gcm = new GCM_SendMsg();

    $res = $db->storeUser($gcm_regid);

    $registatoin_ids = array($gcm_regid);
    $message = array("Hello" => "Zelda");

    $result = $gcm->send_notification($registatoin_ids, $message);

    echo $result;
} else {
    // required user details are not received


10. Create file named device_sendmsg.php, it will be used to send push message to android device by requesting to GCM server.

if (isset($_GET["regId"]) && isset($_GET["message"])) {
    $regId = $_GET["regId"];
    $message = $_GET["message"];

    include_once './gcm_sendmsg.php';

    $gcm = new GCM_SendMsg();

    $registatoin_ids = array($regId);
    $message = array("Hello Zelda" => $message);

    $result = $gcm->send_notification($registatoin_ids, $message);

    echo $result;


11. Create file index.php, it will list all the registered user so far and it will provide simple interface to send push message to registered user.

<!DOCTYPE html>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <script src=""></script>
        <script type="text/javascript">

            function sendPushNotification(id){
                var data = $('form#'+id).serialize();
                    url: "device_sendmsg.php",
                    type: 'GET',
                    data: data,
                    beforeSend: function() {

                    success: function(data, textStatus, xhr) {
                    error: function(xhr, textStatus, errorThrown) {
                return false;
        include_once 'db_functions.php';
        $db = new DB_Functions();
        $users = $db->getAllUsers();
        if ($users != false)
            $no_of_users = mysql_num_rows($users);
            $no_of_users = 0;
        <div >
            <h1>No of Devices Registered: <?php echo $no_of_users; ?></h1>
            <ul class="devices">
                if ($no_of_users > 0) {
                    while ($row = mysql_fetch_array($users)) {
                            <form id="<?php echo $row["id"] ?>" name="" method="post" onsubmit="return sendPushNotification('<?php echo $row["id"] ?>')">
                                <label>RegistrationID: </label> <span><?php echo $row["gcm_regid"] ?></span>
                                <textarea rows="3" name="message" cols="25" class="txt_message" placeholder="Type message here"></textarea>
                                <input type="hidden" name="regId" value="<?php echo $row["gcm_regid"] ?>"/>
                                <input type="submit" class="send_btn" value="Send" onclick=""/>
                    <?php }
                } else { ?>
                        No Users Registered Yet!
                <?php } ?>

We have accomplished Google API console registration and web server configuration. Let move to part 2 for Developing GCM supported Android Application.

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8 Responses

  1. Blair Doyle says:

    I followed this tutorial, and substituted the windows web server with an ubuntu nginx LEMP setup.
    I am running nginx on ubuntu for my webserver w/ php5-fpm.
    confirm PHP is running fine, other php scripts work a-ok on the web server.

    When my android app attempts to register with GCM / Web server , I see “Successfully Registered with GCM” , my web server receives the call to register_user.php , but my web server reports the following error:

    “PHP message: PHP Fatal error: Cannot use isset() on the result of an expression (you can use “null !== expression” instead) in /usr/share/nginx/html/register_user.php on line 9″ while reading response header from upstream, client:, server: localhost, request: “POST /register_user.php HTTP/1.1”, upstream: “fastcgi://unix:/var/run/php5-fpm.sock:”

    Code in question per the tutorial is as follows:

    line 9 —> if (isset(isset($_POST[“regId”])) {
    $gcm_regid = $_POST[“regId”];

    • Blair Doyle says:

      Of course moments after posting I realize that the example code in this tutorial is flawed:

      if (isset(isset($_POST[“regId”])) {
      $gcm_regid = $_POST[“regId”];

      should be:
      if (isset($_POST[“regId”])) {
      $gcm_regid = $_POST[“regId”];

      Not sure how this got missed and more people havn’t raised a flag!.

      Now on to the next issue.. after successful registration, No push notification is sent to the device! doh!

  2. Sandeep Autade says:

    on db_functions.php page having error that table name not matching please correct that
    // insert user into database
    INSERT INTO reg_users

    // check for successful store
    SELECT * FROM users

    thanks for tutorial 🙂

  3. Dharmesh atDuma says:

    returns only “to” value when i execute send push notification

  4. Karthick B says:

    which or what url want set there……

    private static final String WEB_SERVER_URL = “YOUR_WER_SERVER_URL”;

  5. gunjan says:

    Nice tutorial but it runs on android 4.4 when I m tring to execute it on lollypop or marshmallow it will not receive the notification if the app is not running on the background.Pls help me how can I resolve that issue

  1. January 30, 2015

    […] with Google API Console Registration and WebServer Configuration. If not, it is suggested to refer Google API Console Registration and WebServer Configuration before proceeding […]

  2. January 27, 2018

    […] recommend to read the articles Android Push Notification using Google Cloud Messaging (GCM) – Part 1 and Part 2. They are a very good explanation and tutorial how GCM works. Even in this article a […]

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