initialize.java

public void initialize(){

        PeerConnectionFactory.InitializationOptions initializationOptions =
                PeerConnectionFactory.InitializationOptions.builder(context)
                        .createInitializationOptions();
        PeerConnectionFactory.initialize(initializationOptions);

        PeerConnectionFactory.Options options = new PeerConnectionFactory.Options();
        peerConnectionFactory = PeerConnectionFactory.builder().setOptions(options)
                .createPeerConnectionFactory();

        List<PeerConnection.IceServer> iceServers = new ArrayList<>();
        iceServers.add(PeerConnection.IceServer.builder("stun:stun2.1.google.com:19302").createIceServer());
        iceServers.add(PeerConnection.IceServer.builder("turn:numb.viagenie.ca")
                .setUsername("webrtc@live.com")
                .setPassword("muazkh")
                .createIceServer());
        PeerConnection.RTCConfiguration rtcConfig =
                new PeerConnection.RTCConfiguration(iceServers);

        peerConnection = peerConnectionFactory.createPeerConnection(rtcConfig, new CustomPeerConnectionObserver() {

            @Override
            public void onIceCandidate(IceCandidate iceCandidate) {
                super.onIceCandidate(iceCandidate);
                
            }

            @Override
            public void onDataChannel(DataChannel dataChannel) {
                super.onDataChannel(dataChannel);
                
            }

            @Override
            public void onIceConnectionChange(PeerConnection.IceConnectionState iceConnectionState) {
                super.onIceConnectionChange(iceConnectionState);
                if(iceConnectionState != null){
                    
                    if(iceConnectionState == PeerConnection.IceConnectionState.CONNECTED){
                        
                    }
                    if(iceConnectionState == PeerConnection.IceConnectionState.CLOSED){
                        
                    }
                    if(iceConnectionState == PeerConnection.IceConnectionState.FAILED){
                        
                    }
                }
            }
        });

        if(peerConnection == null){
            
            return;
        }

        DataChannel.Init dcInit = new DataChannel.Init();
        dataChannel = peerConnection.createDataChannel("1", dcInit);
        dataChannel.registerObserver(new CustomDataChannelObserver(){

            @Override
            public void onMessage(DataChannel.Buffer buffer) {
                super.onMessage(buffer);
                
            }
        });
    }