     var internalState: PeerChannelInternalState!
     var signalingChannel: SignalingChannel
     var webRTCConfiguration: WebRTCConfiguration!
+    var clientId: String?
     
     var configuration: Configuration {
         get { return channel.configuration }

    
    func peerConnection(_ nativePeerConnection: RTCPeerConnection,
                        didAdd stream: RTCMediaStream) {
        Logger.debug(type: .peerChannel,
                     message: "added a media stream (id: \(stream.streamId))")
        let stream = BasicMediaStream(nativeStream: stream)

            switch message {
            case .offer(let offer):
                Logger.debug(type: .peerChannel, message: "receive offer")
                clientId = offer.clientId
                createAndSendAnswerMessage(offer: offer)
                
            default:
