The protocol version negotiated for this connection (stateful) or the
effective version for the current request (stateless). This is the single
version concept: the server->client push/notification path is driven by
each open listener's own SubscriptionFilter, not by a separate
connection-level version (subscriptions/listen is an ordinary
request and is not special-cased).
The protocol version negotiated for this connection (stateful) or the effective version for the current request (stateless). This is the single version concept: the server->client push/notification path is driven by each open listener's own SubscriptionFilter, not by a separate connection-level version (subscriptions/listen is an ordinary request and is not special-cased).