extractOfferedWsProtocols

Signature

def extractOfferedWsProtocols: Directive1[immutable.Seq[String]]

Description

Extracts the list of WebSocket subprotocols as offered by the client in the Sec-WebSocket-Protocol header if this is a WebSocket request. Rejects with an ExpectedWebSocketRequestRejection, otherwise.

The extractOfferedWsProtocols directive is used as a building block for Custom Directives to provide the extracted protocols to the inner route.

Example

def echoService: Flow[Message, Message, Any] =
  Flow[Message]
    // needed because a noop flow hasn't any buffer that would start processing in tests
    .buffer(1, OverflowStrategy.backpressure)

def route =
  path("services") {
    extractOfferedWsProtocols { protocols =>
      handleWebSocketMessagesForOptionalProtocol(echoService, protocols.headOption)
    }
  }

// tests:
val wsClient = WSProbe()

// WS creates a WebSocket request for testing
WS("/services", wsClient.flow, List("echo", "alfa", "kilo")) ~> route ~> check {
  expectWebSocketUpgradeWithProtocol { protocol =>
    protocol shouldEqual "echo"
    wsClient.sendMessage("ping")
    wsClient.expectMessage("ping")
    wsClient.sendCompletion()
    wsClient.expectCompletion()
  }
}