Stream-Hub send message to specific client

Hello im fairly new to the comet and reverse ajax scene. I discovered stream-hub and it seems very useful.

Reading the documentaions and examples I cant find a way for the server to send a message to a specific client.

I only found the

publish(String topic, Payload payload)

method that broad开发者_开发知识库cast to all users subscribe to the topic

This is what I want EX:

There is 3 users connected User A, User B, and User C

User A sends a message, server receives message and sends to User C, but not User B.

Any ideas?