Ask another session what it is doing
Two sessions are registered: laptop-api (you are here) and server-ci (on another machine).
Hand off a task with a thread id
send takes an optional thread_id. The bus stores it and returns it with the message. It does not interpret it. Use it to keep a request and its replies together.
Broadcast
broadcast sends one body to every other session that is not stale (seen within the last 7 days). The sender is skipped.
Push session or plain session
Both kinds of session use the same bus entry and the same tools. The difference is whether new mail reaches an idle session on its own.
Check who is online
The model calls list_sessions and gets: