Jabber (XMPP) is an open instant messaging protocol used by millions of people daily. With Jabber, you get split-second delivery of new blog posts and comments — for any WordPress.com blog you want to follow. This means there's no need to wait for your RSS feed to update, or to use blog email subscriptions.
Connect to im.wordpress.com – Using Jabber requires that you've a WordPress.com account and use a Jabber client. You'll set up your client with these connection details:
Jabber ID – email@example.com
This is your WordPress.com user name followed by "@im.wordpress.com".
Password, Jabber service uses same password as your WordPress.com account.
Jabber Server/Host – im.wordpress.com
Some clients ask for this; most will figure it out from the Jabber ID.
Port – 5222
This is the usual port for Jabber services. You shouldn't have to enter this.
More Info: Jabber