Saved by xmpp4moz!

After my recent post requesting information about a Firefox-friendly Jabber library, it dawned on me that I should try searching for firefox xmpp library instead of firefox jabber library. Lo and behold, I discovered xmpp4moz! From the project web site, I downloaded the SamePlace Suite Firefox extension, which is a small suite of applications built on top of xmpp4moz. I fired it up and discovered that it contained a nice Jabber client written in XUL with explicit support for Google Talk. The only remaining question was: how did it work?

I checked out the xmpp4moz code from the repository and started looking through it to figure out how it made a secure connection to talk.google.com. I immediately found some code that mentioned the starttls exchange that had thwarted my previous efforts to build a Jabber library for Firefox, but unfortunately it was commented out! After shooting in the dark for awhile with grep, I decided to find the entry point to the sign-on code and step through it.

Two important differences from the Smack library were (1) xmpp4moz connected on port 5223 instead of port 5222, and (2) the initial stanza that it sent to the server included my username and password:

<iq to={JID(jid).hostname} type="set">
  <query xmlns="jabber:iq:auth">
    <username>{JID(jid).username}</username>
    <password>{password}</password>
    <resource>{JID(jid).resource}</resource>
  </query>
</iq>

I found this odd, as this was not what was described in the jabberd 2.0 protocol document I had discovered earlier. I searched on Google to find out what the difference between using ports 5222 and 5223 was, and found out that port 5222 offers TLS support while port 5223 offers SSL support. So by using port 5223, I could connect to Google Talk by using an SSL transport in Firefox, created as follows:

const srvSocketTransport = Components.classes["@mozilla.org/network/socket-transport-service;1"]
    .getService(Components.interfaces.nsISocketTransportService);
var transport = srvSocketTransport.createTransport(['ssl'], 1, "talk.google.com", 5223, null);

From what I have seen of the code so far, xmpp4moz looks to be an organized, well-designed library. I noticed that the developers make generous use of E4X, which is both convenient and brilliant since XMPP messages are in XML: all the more reason to develop a Jabber client within Firefox!

But wait! Didn't I just say that the SamePlace suite already has a nice Jabber client for Firefox? Yes, it certainly does, but I want to explore building an HTML client with some of my own features, so leveraging xmpp4moz looks like the best way to do it!