         self.webSocketChannel = configuration
             ._webSocketChannelType.init(url: configuration.url)
         
-        webSocketChannel!.internalHandlers.onFailureHandler = handleFailure
-        webSocketChannel!.internalHandlers.onMessageHandler = handleMessage
+        webSocketChannel.internalHandlers.onFailureHandler = handleFailure
+        webSocketChannel.internalHandlers.onMessageHandler = handleMessage
     }
     
     func connect(handler: @escaping (Error?) -> Void) {

        default:
            Logger.debug(type: .signalingChannel, message: "try disconnecting")
            state = .disconnecting
            webSocketChannel?.disconnect(error: error)
            state = .disconnected
            if let error = error {
                Logger.debug(type: .signalingChannel, message: "error = \(error)")

    /// クライアントの設定
    var configuration: Configuration { get }
    
    /// WebSocket チャネル
    var webSocketChannel: WebSocketChannel { get }
    
    /// 接続状態
    var state: SignalingChannelState { get }
