Programming Jabber

The XML stream header exchange

Although the XML declaration that is sent immediately preceding the opening <stream:stream/> root tag is optional, it’s not a good idea to leave it out. While the Jabber server currently does not enforce its presence, future implementations may do so.^[1] The Jabber server will always send an XML declaration in response. In both cases—in both streamed XML documents—the encoding is assumed to be UTF-8.

For the most part, the rest of the <stream:stream/> root tag is static. The namespace qualifying the stream content is jabber:client (which is the only namespace acceptable when making such an XML stream connection to the c2s—Client-to-Server—component listening on port 5222), and the namespace qualifying the stream itself is fixed at http://etherx.jabber.org/streams.^[2]

The only thing that is going to be dynamic is the to attribute, which is used to specify the Jabber server name. Note that this is the logical name, the internal name, of the Jabber server. In our example, we’ve already resolved the physical hostname, yak, and connected to port 5222; the to attribute is to specify the virtual Jabber host, which in many cases—including an out-of-the-box jabber.xml configuration—has the same name as the physical host.

If our Jabber server has just a single virtual host, we can use an <alias/> configuration tag in the c2s component instance configuration, as described in Section 4.6.3, to remove the requirement of specifying the to attribute.

Using: ...