There are two examples of chat, using cometd as a backend and Dojo's dojox.cometd client as a transport.
The first, a simple public chat room, that any live participants that happen to be online will be able to communicate.
The other: the example from the Dojo Book - an example of a client / operator relationship, where the client chats from an 'existing' page, and the operator has a TabContainer view of open client chats, and can communicate privately and directly to the client. The client page demonstrates how this can be used in existing pages for real-time support. You will need two people for this, or you are welcome to talk to yourself ...
the Chatroom widget source can be found here.