Android Building Group Chat App using Sockets – Part 1

We have seen a large number of applications come up in the recent past, to help us connect with each other across different mediums, like Hike, Whatsapp, Viber etc. You would be surprised to learn that its rather quite easy to develop one yourself. I thought providing an insight into developing such an application would be helpful for you guys.

Today we are going to learn how to build a simple group chat app using sockets. I won’t say this is the only way to build a chat app, but it is the quick & easiest way to build one. The best and efficient way would be using the push notifications instead of sockets.

android building chat app using java sockets

Overall we are going to build three components in this article. The first and important component is the socket server. The socket server plays a major role like handling the socket client connections, passing the messages between clients. Second component is the web app where you can join the chat conversation from a browser. Finally the android app. The main advantage of this app is, you can chat between web – web, web – android or android – android.

As this article seems pretty much lengthy, I am dividing the tutorial into two parts. In this first part, all the basic setup and building the web app is covered. In the 2nd Part, building the actual android app is covered.

Below are the final outcomes from this tutorial.

android building chat app like whatsapp

How the App Works Over Sockets?

If you are coming across the ‘sockets’ for the first time, the wikipedia page give you basic knowledge about socket communication. Below you can find a brief info about how our app works.

1. First we’ll have a socket server running. When the android app or web app connects to socket server, the server opens a TCP connection between server and client. The server is capable of opening concurrent connections when there are multiple clients.

2. When a socket connection is established few callback methods like onOpen, onMessage, onExit will be triggered on the both the ends (on server side and client side). There will be another method available to send message from client to server, or vice versa.

3. JSON strings will be exchanged between server and client as a communication medium. Each JSON contains a node called flag to identify the purpose of JSON message. Below is example of JSON when a client joined the conversation that contains the client name, session id and number of people online.

{
    "message": " joined conversation!",
    "flag": "new",
    "sessionId": "4",
    "name": "Ravi Tamada",
    "onlineCount": 6
}

4. Whenever a JSON message received on client side, the JSON will be parsed and appropriate action will be taken.

I hope the above information gave enough knowledge over the app. Now we can move forward and start building one by one component.


1. Eclipse adding J2EE & Tomcat 7 Support

The eclipse IDE that comes along with android SDK, doesn’t have J2EE and Tomcat server support. So we have to add J2EE and tomcat extensions. Another option would be downloading another eclipse that supports J2EE, but I would like use the eclipse that supports both android and j2ee instead of two different IDEs.

1. Download apache tomcat 7 from tomcat website. (You can download it from this direct link). Once downloaded, extract it in some location.

2. In Eclipse go to Help ⇒ Install New Software. Click on Work with drop down and select Juno – http://download.eclipse.org/releases/juno. (You might need to select the appropriate eclipse release depending upon your eclipse flavour)

3. Expand Web, XML, Java EE and OSGi Enterprise Development and select below extensions and proceed with installation.
   > Eclipse Java EE Developer Tools
   > JST Server Adapters
   > JST Server Adapters Extensions

4. Once the extensions are installed, Eclipse will prompt you to restart. When the eclipse re-opened, we need to create a server first. Goto Windows ⇒ Show View ⇒ Server ⇒ Servers.

5. In servers tab, click on new server wizard and select Apache ⇒ Tomcat v7.0 Server. Give server name, browse and select the tomcat home directory which we downloaded previously.

Check out the below video if you not very clear with the above steps.


2. Finding Your PC IP Address

As we need to test this app on multiple devices (it can be a mobile, PC or a laptop) in a wifi network, we need to know the IP address of the PC where the socket server project running. So instead of using localhost, we need to use the ip address in the url. In order to get the ip address of your machine, execute below commands in terminal.

On Windows

ipconfig
windows-os-getting-ip-address

On Mac

ifconfig
mac os getting system ip address

Note: The ip address of your machine might changes whenever you disconnected from wifi or a new device added to wifi network. So make sure that you are using the correct ip address every time you test the app.

Once the Eclipse Tomcat setup is ready and you know the IP address, you are good to go with socket server development. Building the socket server is very easy. The socket server we are going to build won’t take more than two class files.

3. Building the Socket Server

1. In Eclipse create a new Dynamic Web Project by navigating to File ⇒ New ⇒ Other ⇒ Web ⇒ Dynamic Web Project. Give the project name and select the Target runtime as Tomcat 7. I gave my project name as WebMobileGroupChatServer.

Once the project is created, it contains below directory structure.

j2ee web dynamic project directory structure

2. Right click on src ⇒ New ⇒ Package and give the package name. I gave my package name as info.androidhive.webmobilegroupchat.

3. Now download google-collections-0.8.jar, javaee-api-7.0.jar, json-org.jar files and paste them in project’s WebContent ⇒ WEB-INF ⇒ lib folder.

4. Create a new class named JSONUtils.java under project’s src package folder. This class contains methods to generate JSON strings those are required to have the communication b/w socket server and clients.

In the below code, if you observer each json contains flag node which tell the clients the purpose of JSON message. On the client side we have to take appropriate action considering the flag value.

Basically the flag contains four values.

self = This JSON contains the session information of that particular client. This will be the first json a client receives when it opens a sockets connection.

new = This JSON broadcasted to every client informing about the new client that is connected to socket server.

message = This contains the message sent by a client to server. Hence it will broadcasted to every client.

exit = The JSON informs every client about the client that is disconnected from the socket server.

package info.androidhive.webmobilegroupchat;

import org.json.JSONException;
import org.json.JSONObject;

public class JSONUtils {

	// flags to identify the kind of json response on client side
	private static final String FLAG_SELF = "self", FLAG_NEW = "new",
			FLAG_MESSAGE = "message", FLAG_EXIT = "exit";

	public JSONUtils() {
	}

	/**
	 * Json when client needs it's own session details
	 * */
	public String getClientDetailsJson(String sessionId, String message) {
		String json = null;

		try {
			JSONObject jObj = new JSONObject();
			jObj.put("flag", FLAG_SELF);
			jObj.put("sessionId", sessionId);
			jObj.put("message", message);

			json = jObj.toString();
		} catch (JSONException e) {
			e.printStackTrace();
		}

		return json;
	}

	/**
	 * Json to notify all the clients about new person joined
	 * */
	public String getNewClientJson(String sessionId, String name,
			String message, int onlineCount) {
		String json = null;

		try {
			JSONObject jObj = new JSONObject();
			jObj.put("flag", FLAG_NEW);
			jObj.put("name", name);
			jObj.put("sessionId", sessionId);
			jObj.put("message", message);
			jObj.put("onlineCount", onlineCount);

			json = jObj.toString();
		} catch (JSONException e) {
			e.printStackTrace();
		}

		return json;
	}

	/**
	 * Json when the client exits the socket connection
	 * */
	public String getClientExitJson(String sessionId, String name,
			String message, int onlineCount) {
		String json = null;

		try {
			JSONObject jObj = new JSONObject();
			jObj.put("flag", FLAG_EXIT);
			jObj.put("name", name);
			jObj.put("sessionId", sessionId);
			jObj.put("message", message);
			jObj.put("onlineCount", onlineCount);

			json = jObj.toString();
		} catch (JSONException e) {
			e.printStackTrace();
		}

		return json;
	}

	/**
	 * JSON when message needs to be sent to all the clients
	 * */
	public String getSendAllMessageJson(String sessionId, String fromName,
			String message) {
		String json = null;

		try {
			JSONObject jObj = new JSONObject();
			jObj.put("flag", FLAG_MESSAGE);
			jObj.put("sessionId", sessionId);
			jObj.put("name", fromName);
			jObj.put("message", message);

			json = jObj.toString();

		} catch (JSONException e) {
			e.printStackTrace();
		}

		return json;
	}
}

5. Create another class named SocketServer.java and add the below code. This is the where we implement actual socket server.

This class mainly contains four callback methods.

onOpen() – This method is called when a new socket client connects.
onMessage() – This method is called when a new message received from the client.
onClose() – This method is called when a socket client disconnected from the server.
sendMessageToAll() – This method is used to broadcast a message to all socket clients.

package info.androidhive.webmobilegroupchat;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

import org.json.JSONException;
import org.json.JSONObject;

import com.google.common.collect.Maps;

@ServerEndpoint("/chat")
public class SocketServer {

	// set to store all the live sessions
	private static final Set<Session> sessions = Collections
			.synchronizedSet(new HashSet<Session>());

	// Mapping between session and person name
	private static final HashMap<String, String> nameSessionPair = new HashMap<String, String>();

	private JSONUtils jsonUtils = new JSONUtils();

	// Getting query params
	public static Map<String, String> getQueryMap(String query) {
		Map<String, String> map = Maps.newHashMap();
		if (query != null) {
			String[] params = query.split("&");
			for (String param : params) {
				String[] nameval = param.split("=");
				map.put(nameval[0], nameval[1]);
			}
		}
		return map;
	}

	/**
	 * Called when a socket connection opened
	 * */
	@OnOpen
	public void onOpen(Session session) {

		System.out.println(session.getId() + " has opened a connection");

		Map<String, String> queryParams = getQueryMap(session.getQueryString());

		String name = "";

		if (queryParams.containsKey("name")) {

			// Getting client name via query param
			name = queryParams.get("name");
			try {
				name = URLDecoder.decode(name, "UTF-8");
			} catch (UnsupportedEncodingException e) {
				e.printStackTrace();
			}

			// Mapping client name and session id
			nameSessionPair.put(session.getId(), name);
		}

		// Adding session to session list
		sessions.add(session);

		try {
			// Sending session id to the client that just connected
			session.getBasicRemote().sendText(
					jsonUtils.getClientDetailsJson(session.getId(),
							"Your session details"));
		} catch (IOException e) {
			e.printStackTrace();
		}

		// Notifying all the clients about new person joined
		sendMessageToAll(session.getId(), name, " joined conversation!", true,
				false);

	}

	/**
	 * method called when new message received from any client
	 * 
	 * @param message
	 *            JSON message from client
	 * */
	@OnMessage
	public void onMessage(String message, Session session) {

		System.out.println("Message from " + session.getId() + ": " + message);

		String msg = null;

		// Parsing the json and getting message
		try {
			JSONObject jObj = new JSONObject(message);
			msg = jObj.getString("message");
		} catch (JSONException e) {
			e.printStackTrace();
		}

		// Sending the message to all clients
		sendMessageToAll(session.getId(), nameSessionPair.get(session.getId()),
				msg, false, false);
	}

	/**
	 * Method called when a connection is closed
	 * */
	@OnClose
	public void onClose(Session session) {

		System.out.println("Session " + session.getId() + " has ended");

		// Getting the client name that exited
		String name = nameSessionPair.get(session.getId());

		// removing the session from sessions list
		sessions.remove(session);

		// Notifying all the clients about person exit
		sendMessageToAll(session.getId(), name, " left conversation!", false,
				true);

	}

	/**
	 * Method to send message to all clients
	 * 
	 * @param sessionId
	 * @param message
	 *            message to be sent to clients
	 * @param isNewClient
	 *            flag to identify that message is about new person joined
	 * @param isExit
	 *            flag to identify that a person left the conversation
	 * */
	private void sendMessageToAll(String sessionId, String name,
			String message, boolean isNewClient, boolean isExit) {

		// Looping through all the sessions and sending the message individually
		for (Session s : sessions) {
			String json = null;

			// Checking if the message is about new client joined
			if (isNewClient) {
				json = jsonUtils.getNewClientJson(sessionId, name, message,
						sessions.size());

			} else if (isExit) {
				// Checking if the person left the conversation
				json = jsonUtils.getClientExitJson(sessionId, name, message,
						sessions.size());
			} else {
				// Normal chat conversation message
				json = jsonUtils
						.getSendAllMessageJson(sessionId, name, message);
			}

			try {
				System.out.println("Sending Message To: " + sessionId + ", "
						+ json);

				s.getBasicRemote().sendText(json);
			} catch (IOException e) {
				System.out.println("error in sending. " + s.getId() + ", "
						+ e.getMessage());
				e.printStackTrace();
			}
		}
	}
}

With this we have completed the socket server part. Now quickly we can build a web app to the test the socket server. Again building the web app is very simple. The complete web app can be built using basic web technologies like HTML, CSS & jQuery.

4. Building The Web App (HTML, CSS & jQuery)

To create the web app, we don’t have to create another project. This is the part of same socket server project, so follow the below steps in the same project.

1. Create a file named style.css under WebContent ⇒ WEB-INF folder. This contains the css styles for the web UI.

body {
	padding: 0;
	margin: 0;
}

.body_container {
	width: 1000px;
	margin: 0 auto;
	padding: 0;
}

.clear {
	clear: both;
}

.green {
	color: #8aaf0d;
}

#header {
	margin: 0 auto;
	padding: 50px 0;
	text-align: center;
}

#header h1,#header p.online_count {
	font-family: 'Open Sans', sans-serif;
	font-weight: 300;
}

#header p.online_count {
	font-size: 18px;
	display: none;
}

.box_shadow {
	background: #f3f4f6;
	border: 1px solid #e4e4e4;
	-moz-box-shadow: 0px 0px 2px 1px #e5e5e5;
	-webkit-box-shadow: 0px 0px 2px 1px #e5e5e5;
	box-shadow: 0px 0px 2px 1px #e5e5e5;
}

#prompt_name_container {
	margin: 0 auto;
	width: 350px;
	text-align: center;
}

#prompt_name_container p {
	font-family: 'Open Sans', sans-serif;
	font-weight: 300;
	font-size: 24px;
	color: #5e5e5e;
}

#prompt_name_container #input_name {
	border: 1px solid #dddddd;
	padding: 10px;
	width: 250px;
	display: block;
	margin: 0 auto;
	outline: none;
	font-family: 'Open Sans', sans-serif;
}

#prompt_name_container #btn_join {
	border: none;
	width: 100px;
	display: block;
	outline: none;
	font-family: 'Open Sans', sans-serif;
	color: #fff;
	background: #96be0e;
	font-size: 18px;
	padding: 5px 20px;
	margin: 15px auto;
	cursor: pointer;
}

#message_container {
	display: none;
	width: 500px;
	margin: 0 auto;
	background: #fff;
	padding: 15px 0 0 0;
}

#messages {
	margin: 0;
	padding: 0;
	height: 300px;
	overflow: scroll;
	overflow-x: hidden;
}

#messages li {
	list-style: none;
	font-family: 'Open Sans', sans-serif;
	font-size: 16px;
	padding: 10px 20px;
}

#messages li.new,#messages li.exit {
	font-style: italic;
	color: #bbbbbb;
}

#messages li span.name {
	color: #8aaf0d;
}

#messages li span.red {
	color: #e94e59;
}

#input_message_container {
	margin: 40px 20px 0 20px;
}

#input_message {
	background: #f0f0f0;
	border: none;
	font-size: 20px;
	font-family: 'Open Sans', sans-serif;
	outline: none;
	padding: 10px;
	float: left;
	margin: 0;
	width: 348px;
}

#btn_send {
	float: left;
	margin: 0;
	border: none;
	color: #fff;
	font-family: 'Open Sans', sans-serif;
	background: #96be0e;
	outline: none;
	padding: 10px 20px;
	font-size: 20px;
	cursor: pointer;
}

#btn_close {
	margin: 0;
	border: none;
	color: #fff;
	font-family: 'Open Sans', sans-serif;
	background: #e94e59;
	outline: none;
	padding: 10px 20px;
	font-size: 20px;
	cursor: pointer;
	width: 100%;
	margin: 30px 0 0 0;
}

2. Create another file named main.js and add below javascript. This file contains all the methods required to handle communication between socket server and client. The other things like parsing JSON, appending messages to chat list also taken care in the same file.

// to keep the session id
var sessionId = '';

// name of the client
var name = '';

// socket connection url and port
var socket_url = '192.168.0.102';
var port = '8080';

$(document).ready(function() {

	$("#form_submit, #form_send_message").submit(function(e) {
		e.preventDefault();
		join();
	});
});

var webSocket;

/**
 * Connecting to socket
 */
function join() {
	// Checking person name
	if ($('#input_name').val().trim().length <= 0) {
		alert('Enter your name');
	} else {
		name = $('#input_name').val().trim();

		$('#prompt_name_container').fadeOut(1000, function() {
			// opening socket connection
			openSocket();
		});
	}

	return false;
}

/**
 * Will open the socket connection
 */
function openSocket() {
	// Ensures only one connection is open at a time
	if (webSocket !== undefined && webSocket.readyState !== WebSocket.CLOSED) {
		return;
	}

	// Create a new instance of the websocket
	webSocket = new WebSocket("ws://" + socket_url + ":" + port
			+ "/WebMobileGroupChatServer/chat?name=" + name);

	/**
	 * Binds functions to the listeners for the websocket.
	 */
	webSocket.onopen = function(event) {
		$('#message_container').fadeIn();

		if (event.data === undefined)
			return;

	};

	webSocket.onmessage = function(event) {

		// parsing the json data
		parseMessage(event.data);
	};

	webSocket.onclose = function(event) {
		alert('Error! Connection is closed. Try connecting again.');
	};
}

/**
 * Sending the chat message to server
 */
function send() {
	var message = $('#input_message').val();

	if (message.trim().length > 0) {
		sendMessageToServer('message', message);
	} else {
		alert('Please enter message to send!');
	}

}

/**
 * Closing the socket connection
 */
function closeSocket() {
	webSocket.close();

	$('#message_container').fadeOut(600, function() {
		$('#prompt_name_container').fadeIn();
		// clearing the name and session id
		sessionId = '';
		name = '';

		// clear the ul li messages
		$('#messages').html('');
		$('p.online_count').hide();
	});
}

/**
 * Parsing the json message. The type of message is identified by 'flag' node
 * value flag can be self, new, message, exit
 */
function parseMessage(message) {
	var jObj = $.parseJSON(message);

	// if the flag is 'self' message contains the session id
	if (jObj.flag == 'self') {

		sessionId = jObj.sessionId;

	} else if (jObj.flag == 'new') {
		// if the flag is 'new', a client joined the chat room
		var new_name = 'You';

		// number of people online
		var online_count = jObj.onlineCount;

		$('p.online_count').html(
				'Hello, <span class="green">' + name + '</span>. <b>'
						+ online_count + '</b> people online right now')
				.fadeIn();

		if (jObj.sessionId != sessionId) {
			new_name = jObj.name;
		}

		var li = '<li class="new"><span class="name">' + new_name + '</span> '
				+ jObj.message + '</li>';
		$('#messages').append(li);

		$('#input_message').val('');

	} else if (jObj.flag == 'message') {
		// if the json flag is 'message', it means somebody sent the chat
		// message

		var from_name = 'You';

		if (jObj.sessionId != sessionId) {
			from_name = jObj.name;
		}

		var li = '<li><span class="name">' + from_name + '</span> '
				+ jObj.message + '</li>';

		// appending the chat message to list
		appendChatMessage(li);

		$('#input_message').val('');

	} else if (jObj.flag == 'exit') {
		// if the json flag is 'exit', it means somebody left the chat room
		var li = '<li class="exit"><span class="name red">' + jObj.name
				+ '</span> ' + jObj.message + '</li>';

		var online_count = jObj.onlineCount;

		$('p.online_count').html(
				'Hello, <span class="green">' + name + '</span>. <b>'
						+ online_count + '</b> people online right now');

		appendChatMessage(li);
	}
}

/**
 * Appending the chat message to list
 */
function appendChatMessage(li) {
	$('#messages').append(li);

	// scrolling the list to bottom so that new message will be visible
	$('#messages').scrollTop($('#messages').height());
}

/**
 * Sending message to socket server message will be in json format
 */
function sendMessageToServer(flag, message) {
	var json = '{""}';

	// preparing json object
	var myObject = new Object();
	myObject.sessionId = sessionId;
	myObject.message = message;
	myObject.flag = flag;

	// converting json object to json string
	json = JSON.stringify(myObject);

	// sending message to server
	webSocket.send(json);
}

3. Now download jquery-1.11.1.min and the paste the file in WebContent ⇒ WEB-INF.

4. Finally create another file named index.html and add below code.

<!DOCTYPE html>

<html>
<head>
<title>Android, WebSockets Chat App | AndroidHive
	(www.androidhive.info)</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width">
<script type="text/javascript" src="jquery-1.11.1.min.js"></script>
<link
	href='http://fonts.googleapis.com/css?family=Open+Sans:400,600,300,700'
	rel='stylesheet' type='text/css'>
<link href="style.css" type="text/css" rel='stylesheet' />
<script type="text/javascript" src="main.js"></script>
</head>
<body>
	<div class="body_container">

		<div id="header">
			<h1>Android WebSockets Chat Application</h1>
			<p class='online_count'>
				<b>23</b> people online right now
			</p>
		</div>

		<div id="prompt_name_container" class="box_shadow">
			<p>Enter your name</p>
			<form id="form_submit" method="post">
				<input type="text" id="input_name" /> <input type="submit"
					value="JOIN" id="btn_join">
			</form>
		</div>

		<div id="message_container" class="box_shadow">

			<ul id="messages">
			</ul>


			<div id="input_message_container">
				<form id="form_send_message" method="post" action="#">
					<input type="text" id="input_message"
						placeholder="Type your message here..." /> <input type="submit"
						id="btn_send" onclick="send();" value="Send" />
					<div class="clear"></div>
				</form>
			</div>
			<div>

				<input type="button" onclick="closeSocket();"
					value="Leave Chat Room" id="btn_close" />
			</div>

		</div>

	</div>

</body>
</html>

5. Now run the project by Right Click on project ⇒ Run As ⇒ Run on Server. You can see the project running on http://localhost:8080/WebMobileGroupChatServer/

5. Testing The Socket Server (using the web app)

In order to test the socket server using the web app, follow below steps. You can use multiple devices (like desktop PC, Laptop) or just one machine is enough.

1. Make sure that all the machines connected to same wifi router if you are testing the app on multiple machines. If you are testing the app using a single computer, you don’t have to connect to a wifi network.

2. Find the IP address of the machine on which socket server project is running. (Follow the steps mentioned in 2nd point to get the ip address)

3. Replace the ip address in main.js with your machine’s ip address.

var socket_url = '_YOUR_IP_ADDRESS_';

4. Now access your project url in browser. Replace localhost with your machine ip address in the url. My project url is http://192.168.0.104:8080/WebMobileGroupChatServer/. Access same url in another browser software or another machine’s browser to chat with different machines.


Once you are able to chat between multiple clients, we can go forward and build the android app in Android Building Group Chat App using Sockets – Part 2

Ravi is hardcore Android programmer and Android programming has been his passion since he compiled his first hello-world program. Solving real problems of Android developers through tutorials has always been interesting part for him.