HOMEGCMAndroid Building Realtime Chat App using GCM, PHP & MySQL – Part 1 Android Building Realtime Chat App using GCM, PHP & MySQL – Part 1

Ref : http://www.androidhive.info/2016/02/android-push-notifications-using-gcm-php-mysql-realtime-chat-app-part-1/

Google Cloud Messaging allows you send lightweight messages from the backend server to all the devices whenever there is new data available. This saves lot of user’s battery by avoiding poll request to server for new data. Using GCM you can build powerful multi platform (iOS, Android & Web) apps like real time chat, news feed, cloud storage and lot more. On top of everything, GCM is completely free and there are no limitations.

As parse.com announced their shutdown recently, GCM is the only best option even though it won’t comes with an admin interface. But don’t worry, we’ll build a simple admin panel in this article.

As this article is pretty lengthy, I have divided it into 3 parts. Each part covers a unique part in building the final realtime chat app.

Part 1: Covers building the REST API for chat app including the GCM server app.

Part 2: Explains integrating GCM into your android app including a test message.

Part 3: Building Simple Realtime Chat App.

1. Google Cloud Messaging

Typically GCM implementation involves three components. Google cloud messaging server, the app server and the client app. We should take care of writing the app server and the client app. In order to make calls from the app server to GCM server, you can follow HTTP or XMPP protocol. HTTP supports downstream (gcm to client) messages only. XMPP supports both downstream and upstream (device to gcm, then from gcm to server) messages.

Below is the pictorial representation of the overall architecture.

1. First the app connects to GCM server and register itself.

2. Upon successful registration, GCM issues gcm registration token to device. This registration token uniquely identifies each device.

3. The device sends the registration token to our server to store it in MySQL.

4. Whenever app server wants to send push notification, it sends a request to GCM server sending the push message along with the registration token.

5. GCM server identifies the device using the registration token and initiates the push message.

6. The device receives the push messages and further action takes place.

2. Obtaining Google API Key

Google API key is necessary to interact with GCM server. GCM uses this key to identify your server app. Follow the below steps to obtain your API key. Note that the developer console interface is changing more frequently. So, the below steps may vary in future.

1. Goto Google developers console and create a new app. If you have already created one, select the app.

2. Give a name to your new project. Once the project is created, go to project’s dashboard and click on Use Google APIs

3. Under Mobile APIs, click on Cloud Messaging for Android and enable the API by clicking on top enable API button.

4. Once enabled, click on Credentials on the left. You will be asked to create new credentials by showing multiple options. Choose API Key and then Server Key.

5. After choosing Server Key, your API key will be displayed on the dashboard. Note down the API key as we need to use it in our PHP project.

3. Building Simple Realtime Chat App

In this article, we are going to learn how to create a simple realtime chat app by using Android, GCM, PHP, MySQL, HTML & CSS. We use HTML & CSS to build the admin panel for the server app.

Below are the screens of the android app.

And the server app comes with the option of choosing the user(s) / topic and send the push notification.

This part of the article involves building the server app including designing the MySQL database, REST API for mobile app and an admin panel to send push notifications. I am using Netbeans IDE to develop the PHP code andWAMP / MAMP server to create the php, mysql environment.

Now let’s start designing the database first.

4. Designing MySQL Database

For this app we need only three tables. users, chat rooms and messages.

users – This table holds the user information like name, email and other profile information along with gcm registration id.

chat_rooms – Contains the chat room information.

messages – Contains the messages sent in the chat rooms.

Open phpmyadmin and execute the below sql query to create the required database and tables.

CREATE DATABASE gcm_chat;

 

CREATE TABLE `chat_rooms` (

  `chat_room_id` int(11) NOT NULL,

  `name` varchar(100) NOT NULL,

  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP

) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;

 

CREATE TABLE `messages` (

  `message_id` int(11) NOT NULL,

  `chat_room_id` int(11) NOT NULL,

  `user_id` int(11) NOT NULL,

  `message` text NOT NULL,

  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP

) ENGINE=InnoDB DEFAULT CHARSET=latin1;

 

CREATE TABLE `users` (

  `user_id` int(11) NOT NULL,

  `name` varchar(255) NOT NULL,

  `email` varchar(255) NOT NULL,

  `gcm_registration_id` text NOT NULL,

  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP

) ENGINE=InnoDB DEFAULT CHARSET=latin1;

 

ALTER TABLE `chat_rooms`

  ADD PRIMARY KEY (`chat_room_id`);

 

ALTER TABLE `messages`

  ADD PRIMARY KEY (`message_id`),

  ADD KEY `chat_room_id` (`chat_room_id`),

  ADD KEY `user_id` (`user_id`),

  ADD KEY `chat_room_id_2` (`chat_room_id`);

 

ALTER TABLE `users`

  ADD PRIMARY KEY (`user_id`),

  ADD UNIQUE KEY `email` (`email`);

 

ALTER TABLE `messages`

  ADD CONSTRAINT `messages_ibfk_3` FOREIGN KEY (`chat_room_id`) REFERENCES `chat_rooms` (`chat_room_id`),

  ADD CONSTRAINT `messages_ibfk_2` FOREIGN KEY (`user_id`) REFERENCES `users` (`user_id`) ON DELETE CASCADE ON UPDATE CASCADE;

5. Creating PHP REST API

I am using Slim framework to create the REST endpoints. If you are not aware of PHP Slim, refer my previous tutorial REST API for Android app using PHP, Slim and MySQL to understand how easily you can create the REST API endpoints for your android app.

Below is the project structure of the PHP app. You have to make sure that you are following same structure while following the further steps.