The context hashmap

The context hashmap contains:

• The session atom
• Some I/O related functions which are use-case specific and that the user has to provide.
• The :send-message function
• The :close-connection function

The context hashmap is also used for passing the current message to be processed to the event handlers.

Context vs. session

The difference between the context and the session is that the session is a mutable state (an atom) being shared by all the event handlers, while the context is an immutable Clojure value contains contextual information, like the current message being processed.

You can add your own data in either the context or the session if it makes sense for you, all the message handlers and the user callbacks are called with the context as their first (and only) argument.