handleWebSocketMessagesForOptionalProtocol

def handleWebSocketMessagesForOptionalProtocol( handler: Flow[Message, Message, Any], subprotocol: Option[String]): Route 
def handleWebSocketMessagesForOptionalProtocol( handler: Flow[Message, Message, Any], subprotocol: Option[String], shouldCompress: Message 

Description

Handles WebSocket requests with the given handler and rejects other requests with an ExpectedWebSocketRequestRejectionExpectedWebSocketRequestRejection.

If the subprotocol parameter is Noneempty any WebSocket request is accepted. If the subprotocol parameter is Some(protocol)a non-empty Optional a WebSocket request is only accepted if the list of subprotocols supported by the client (as announced in the WebSocket request) contains protocolmatches the contained subprotocol. If the client did not offer the protocol in question the request is rejected with an UnsupportedWebSocketSubprotocolRejectionUnsupportedWebSocketSubprotocolRejection.

The overload that accepts a shouldCompress filter can select compression separately for each outbound message after permessage-deflate is negotiated. It is evaluated synchronously once for each outbound text or binary message, and its result applies to every fragment of that message. The filter is not invoked for control frames or when compression was not negotiated. It should be fast and non-blocking; throwing from it fails the WebSocket stream.

For a streamed message, the complete payload and its final size are not available when the filter is evaluated. Applications that select compression based on message size therefore need an explicit policy for streamed messages.

To support several subprotocols you may chain several handleWebSocketMessagesForOptionalProtocol routes.

The handleWebSocketMessagesForOptionalProtocol directive is used as a building block for WebSocket Directives to handle websocket messages.

For more information about the WebSocket support, see Server-Side WebSocket Support.