XMPP IM with Smack for Java applications – Infrastructure for Instant Messaging

This tutorial is the third part of the “Setting up an infrastructure for Instant Messaging” article series. In my previous tutorials, I showed you how to setup the Openfire IM Server and how to configure the Spark client in order to connect to that server. In this tutorial, I will show you how to add XMPP messaging capabilities to your own application.

I will use the Smack library, an Open Source XMPP (Jabber) client library for instant messaging and presence. Smack is a pure Java library and can be embedded into your applications to create anything from a full XMPP client to simple XMPP integrations.

XMPP is a simple XML protocol. Under the hood, XML messages are transmitted from the server to the client and vice versa. However, you don’t have to deal with those low level details, unless you want to. Smack hides all these via a well designed API. You can take a first hint of how the API works by reading the article “Instant Messaging in Java Made Easy: The Smack API”. I believe that you are familiar with the concept of instant messaging in general, so we are ready to write some code.

First download the library from the Ignite Realtime site. Since Smack is written in Java, it is cross-platform. The current version is 3.1.0 and I downloaded the tar.gz version (direct download here). After you extract the bundle file, you will find the library JARs along with the corresponding Javadocs. The online Javadocs can be found here (bookmark it to your favorite browser).

Create a new Eclipse project, let’s say under the name “XMPPProject”, and add the “smack.jar” and “smackx.jar” files into your classpath.

The main class that your client will use is XMPPConnection. As the name implies, it represents an XMPP connection to a remote server. Creating a connection and performing a login is as simple as the following code snippet:

// Create a connection to the igniterealtime.org XMPP server.
XMPPConnection connection = new XMPPConnection("myxmppserver.com");
// Connect to the server
connection.connect();
// Most servers require you to login before performing other tasks.
connection.login("myuser", "mypass");

Of course, a more sophisticated configuration of the connection attributes is possible and that can be achieved by using the ConnectionConfiguration class. There are multiple parameters that can be configured, with the most significant being the server host and port and various security (encryption) issues. You can also configure the internal Smack stack by using the SmackConfiguration class.

ConnectionConfiguration config = 
     new ConnectionConfiguration(serverHost, serverPort);
XMPPConnection connection = new XMPPConnection(config);
connection.connect();
connection.login("myuser", "mypass");

From a valid XMPPConnection, you can retrieve a ChatManager object. This one keeps track of references to all current chats and allows you to create Chat instances, i.e. series of messages sent between two users. Chat object are able of sending messages to other chat participants. You can use plain strings or construct XMPP message packets, represented by the Message class. Message class provides direct access to all of the message attributes, such as the message type. For processing incoming messages, you have to implement the MessageListener interface and attach it to a chat.

ChatManager chatManager = connection.getChatManager();
Chat chat = chatManager.createChat("mybuddy", new MyMessageListener());
chat.sendMessage(message);

You can also set your online status, also known as presence, by using the Presence class.

Presence presence = new Presence(Presence.Type.available);
presence.setStatus("What's up everyone?");
connection.sendPacket(presence);

A new buddy can be added to your list by using the Roster class. A user’s roster is a collection of users a person receives presence updates for. A user can be associated with groups, but in the following example the new roster entry won’t belong to a group.

Roster roster = connection.getRoster();
roster.createEntry(user, name, null);

The main class I created is named “XmppManager” and the source code is the following:

package com.javacodegeeks.xmpp;

import org.jivesoftware.smack.Chat;
import org.jivesoftware.smack.ChatManager;
import org.jivesoftware.smack.ConnectionConfiguration;
import org.jivesoftware.smack.MessageListener;
import org.jivesoftware.smack.Roster;
import org.jivesoftware.smack.SmackConfiguration;
import org.jivesoftware.smack.XMPPConnection;
import org.jivesoftware.smack.XMPPException;
import org.jivesoftware.smack.ConnectionConfiguration.SecurityMode;
import org.jivesoftware.smack.packet.Message;
import org.jivesoftware.smack.packet.Presence;
import org.jivesoftware.smack.packet.Presence.Type;

public class XmppManager {
    
    private static final int packetReplyTimeout = 500; // millis
    
    private String server;
    private int port;
    
    private ConnectionConfiguration config;
    private XMPPConnection connection;

    private ChatManager chatManager;
    private MessageListener messageListener;
    
    public XmppManager(String server, int port) {
        this.server = server;
        this.port = port;
    }
    
    public void init() throws XMPPException {
        
        System.out.println(String.format("Initializing connection to server %1$s port %2$d", server, port));

        SmackConfiguration.setPacketReplyTimeout(packetReplyTimeout);
        
        config = new ConnectionConfiguration(server, port);
        config.setSASLAuthenticationEnabled(false);
        config.setSecurityMode(SecurityMode.disabled);
        
        connection = new XMPPConnection(config);
        connection.connect();
        
        System.out.println("Connected: " + connection.isConnected());
        
        chatManager = connection.getChatManager();
        messageListener = new MyMessageListener();
        
    }
    
    public void performLogin(String username, String password) throws XMPPException {
        if (connection!=null && connection.isConnected()) {
            connection.login(username, password);
        }
    }

    public void setStatus(boolean available, String status) {
        
        Presence.Type type = available? Type.available: Type.unavailable;
        Presence presence = new Presence(type);
        
        presence.setStatus(status);
        connection.sendPacket(presence);
        
    }
    
    public void destroy() {
        if (connection!=null && connection.isConnected()) {
            connection.disconnect();
        }
    }
    
    public void sendMessage(String message, String buddyJID) throws XMPPException {
        System.out.println(String.format("Sending mesage '%1$s' to user %2$s", message, buddyJID));
        Chat chat = chatManager.createChat(buddyJID, messageListener);
        chat.sendMessage(message);
    }
    
    public void createEntry(String user, String name) throws Exception {
        System.out.println(String.format("Creating entry for buddy '%1$s' with name %2$s", user, name));
        Roster roster = connection.getRoster();
        roster.createEntry(user, name, null);
    }
    
    class MyMessageListener implements MessageListener {

        @Override
        public void processMessage(Chat chat, Message message) {
            String from = message.getFrom();
            String body = message.getBody();
            System.out.println(String.format("Received message '%1$s' from %2$s", body, from));
        }
        
    }
    
}

Note that no security authentication is used and that the security mode is disabled. That means that there is no protection on the credentials exchange and that the messages are not secured. Smack API supports encryption, but I did not use it since I wanted to keep this tutorial simple.

Ok, let’s see how all the above can be combined in order to create a simple IM application. I will be using the Openfire server installed in a previous tutorial, along with the two users that were created.

First, I use my Spark client to login as user “testuser2”. Nothing special here. Next, I am creating a test class that uses “XmppManager”, connects to my Openfire server, logins as user “testuser1”, sets the online status to “available”, adds the “testuser2” to the roster and finally sends a message. Note that I created an infinite loop so that I can send messages from the Spark client and see them to my console. I am using the “isRunning” boolean to continue the looping. In a real application, this would be set to false if the program was to exit. Make sure you set the thread to sleep for some time, else your machine’s CPU will hit the roof. The test class is the following:

package com.javacodegeeks.xmpp;

public class XmppTest {
    
    public static void main(String[] args) throws Exception {
        
        String username = "testuser1";
        String password = "testuser1pass";
        
        XmppManager xmppManager = new XmppManager("myserver", 5222);
        
        xmppManager.init();
        xmppManager.performLogin(username, password);
        xmppManager.setStatus(true, "Hello everyone");
        
        String buddyJID = "testuser2";
        String buddyName = "testuser2";
        xmppManager.createEntry(buddyJID, buddyName);
        
        xmppManager.sendMessage("Hello mate", "testuser2@myserver");
        
        boolean isRunning = true;
        
        while (isRunning) {
            Thread.sleep(50);
        }
        
        xmppManager.destroy();
        
    }

}

Make sure you select the appropriate username/password and server settings.

If you run the program, you should see the incoming message to the Spark client. Answer to that message and then check your Eclipse console to ensure that the message was printed.

Note that “testuser2” received the message even though he hadn’t added “testuser1” as his buddy. This is the default behavior. Add the other user by hitting the “Add a Contact” button.

After the account is added, you will be able to see if the user is online and his current status as well.

Finally, you can retrieve the user’s roster and check the status of the existing contacts.

public void printRoster() throws Exception {
 Roster roster = connection.getRoster();
 Collection<RosterEntry> entries = roster.getEntries();  
 for (RosterEntry entry : entries) {
  System.out.println(String.format("Buddy:%1$s - Status:%2$s", 
      entry.getName(), entry.getStatus()));
 }
}

That’s all! As always, the Eclipse project created can be found here.

Happy coding!!!

• Openfire server installation
• Openfire server configuration

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