Question

may i know what integration technique that you folks use to implement external component to an existing XMPP server (e.g. ejabberd or OpenFire) . Is it through sending xmpp message to another user@externaldomain directly or using mechanism like urlfetch?

Answer 1

Google app engine (Gae) does support XMPP just as CLIENT.

With XMPP Gae JAVA client feature you can:

SEND MESSAGE

JID jid = new JID("[e-mail]");
Message msg = new MessageBuilder()
    .withRecipientJids(jid)
    .withBody("Hello i'm a fancy GAE app, how are you?")
    .build();                    
XMPPService xmpp = XMPPServiceFactory.getXMPPService();
if (xmpp.getPresence(jid).isAvailable()) {
   SendResponse status = xmpp.sendMessage(msg);               
}

RECEIVE MESSAGE

public class XMPPReceiverServlet extends HttpServlet {
  public void doPost(HttpServletRequest req, HttpServletResponse res)
          throws IOException {
    XMPPService xmpp = XMPPServiceFactory.getXMPPService();
    Message message = xmpp.parseMessage(req);    
    JID fromJid = message.getFromJid();
    String body = message.getBody();
    //Save to Big Table
  }
}

Remember that JIDs can just be [e-mail] OR [e-mail]
because Google domains are not supported yet.

For example, you could craft a toy Gae application with a simple page with:

1. An html form to send text
2. An html table that display the list of messages received and stored to big table.

To test your application:

1. Create an account on jabber.org
2. Download Smack
3. Try to send a message from Smack to [e-mail]
4. Try to send a message from Gae App to [e-mail]

In case you have your personal XMPP server (openfire) up and running, simply skip step 1 and use your domain account to receive message from your fancy Gae App.

Have a look to XMPP message delivery to understand how this works.