websocket sub-protocol: https://github.com/enisdenjo/graphql-ws/blob/master/PROTOCOL.md.

websocket sub-protocol: https://github.com/apollographql/subscriptions-transport-ws/blob/master/PROTOCOL.md.

SubscriptionClient allows running multiple subscriptions via the same WebSocket either SSE connection It takes care of de-duplicating connections to the same origin under certain circumstances If Hash(URL,Body,Headers) result in the same result, an existing connection is re-used.

GraphQLSubscriptionClientFactory abstracts the way of creating a new GraphQLSubscriptionClient.