SimplePeerActivity.java

public void start() {
    //Initialize PeerConnectionFactory globals.
    //Params are context, initAudio,initVideo and videoCodecHwAcceleration
    PeerConnectionFactory.initializeAndroidGlobals(this, true, true, true);

    //Create a new PeerConnectionFactory instance.
    PeerConnectionFactory.Options options = new PeerConnectionFactory.Options();
    peerConnectionFactory = new PeerConnectionFactory(options);

    //Now create a VideoCapturer instance. Callback methods are there if you want to do something! Duh!
    VideoCapturer videoCapturerAndroid = getVideoCapturer(new CustomCameraEventsHandler());

    //Create MediaConstraints - Will be useful for specifying video and audio constraints.
    audioConstraints = new MediaConstraints();
    videoConstraints = new MediaConstraints();

    //Create a VideoSource instance
    videoSource = peerConnectionFactory.createVideoSource(videoCapturerAndroid, videoConstraints);
    localVideoTrack = peerConnectionFactory.createVideoTrack("100", videoSource);

    //create an AudioSource instance
    audioSource = peerConnectionFactory.createAudioSource(audioConstraints);
    localAudioTrack = peerConnectionFactory.createAudioTrack("101", audioSource);
    localVideoView.setVisibility(View.VISIBLE);

    //create a videoRenderer based on SurfaceViewRenderer instance
    localRenderer = new VideoRenderer(localVideoView);
    // And finally, with our VideoRenderer ready, we
    // can add our renderer to the VideoTrack.
    localVideoTrack.addRenderer(localRenderer);
}

private void call() {
    //we already have video and audio tracks. Now create peerconnections
    List<PeerConnection.IceServer> iceServers = new ArrayList<>();

    //create sdpConstraints
    sdpConstraints = new MediaConstraints();
    sdpConstraints.mandatory.add(new MediaConstraints.KeyValuePair("offerToReceiveAudio", "true"));
    sdpConstraints.mandatory.add(new MediaConstraints.KeyValuePair("offerToReceiveVideo", "true"));

    //creating localPeer
    localPeer = peerConnectionFactory.createPeerConnection(iceServers, sdpConstraints, new CustomPeerConnectionObserver("localPeerCreation") {
        @Override
        public void onIceCandidate(IceCandidate iceCandidate) {
            super.onIceCandidate(iceCandidate);
            onIceCandidateReceived(localPeer, iceCandidate);
        }
    });

    //creating remotePeer
    remotePeer = peerConnectionFactory.createPeerConnection(iceServers, sdpConstraints, new CustomPeerConnectionObserver("remotePeerCreation") {

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

        @Override
        public void onAddStream(MediaStream mediaStream) {
            super.onAddStream(mediaStream);
            gotRemoteStream(mediaStream);
        }
    });

    //creating local mediastream
    MediaStream stream = peerConnectionFactory.createLocalMediaStream("102");
    stream.addTrack(localAudioTrack);
    stream.addTrack(localVideoTrack);
    localPeer.addStream(stream);

    //creating Offer
    localPeer.createOffer(new CustomSdpObserver("localCreateOffer"){
        @Override
        public void onCreateSuccess(SessionDescription sessionDescription) {
            //we have localOffer. Set it as local desc for localpeer and remote desc for remote peer.
            //try to create answer from the remote peer.
            super.onCreateSuccess(sessionDescription);
            localPeer.setLocalDescription(new CustomSdpObserver("localSetLocalDesc"), sessionDescription);
            remotePeer.setRemoteDescription(new CustomSdpObserver("remoteSetRemoteDesc"), sessionDescription);
            remotePeer.createAnswer(new CustomSdpObserver("remoteCreateOffer") {
                @Override
                public void onCreateSuccess(SessionDescription sessionDescription) {
                    //remote answer generated. Now set it as local desc for remote peer and remote desc for local peer.
                    super.onCreateSuccess(sessionDescription);
                    remotePeer.setLocalDescription(new CustomSdpObserver("remoteSetLocalDesc"), sessionDescription);
                    localPeer.setRemoteDescription(new CustomSdpObserver("localSetRemoteDesc"), sessionDescription);
                }
            },new MediaConstraints());
        }
    },sdpConstraints);
}


private void hangup() {
    localPeer.close();
    remotePeer.close();
    localPeer = null;
    remotePeer = null;
}

private void gotRemoteStream(MediaStream stream) {
    //we have remote video stream. add to the renderer.
    final VideoTrack videoTrack = stream.videoTracks.getFirst();
    AudioTrack audioTrack = stream.audioTracks.getFirst();
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            try {
                remoteRenderer = new VideoRenderer(remoteVideoView);
                remoteVideoView.setVisibility(View.VISIBLE);
                videoTrack.addRenderer(remoteRenderer);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

public void onIceCandidateReceived(PeerConnection peer, IceCandidate iceCandidate) {
    //we have received ice candidate. We can set it to the other peer.
    if (peer == localPeer) {
        remotePeer.addIceCandidate(iceCandidate);
    } else {
        localPeer.addIceCandidate(iceCandidate);
    }
}