wAsync throws ClassNotFondException

I have been trying to write an android client for the OpenHab server using wAsync.

I am using android studio with sdk version 21.

my code:

import android.os.StrictMode;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;

import android.view.View;
import android.widget.Button;

import android.widget.TextView;

import org.atmosphere.wasync.ClientFactory;
import org.atmosphere.wasync.Decoder;
import org.atmosphere.wasync.Encoder;
import org.atmosphere.wasync.Event;
import org.atmosphere.wasync.Function;
import org.atmosphere.wasync.Request;
import org.atmosphere.wasync.RequestBuilder;
import org.atmosphere.wasync.Socket;
import org.atmosphere.wasync.impl.AtmosphereClient;
import org.codehaus.jackson.map.ObjectMapper;

import android.os.Handler;

import java.io.IOException;


public class MainActivity extends ActionBarActivity {

private Button act;
private TextView view;
private final String serverIp="http://demo.openhab.org:8080/rest/items/DemoSwitch/state";
private final static ObjectMapper mapper=new ObjectMapper();
private final Handler uiHandler=new Handler();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);

    setContentView(R.layout.activity_main);

    act = (Button) findViewById(R.id.act);
    view = (TextView) findViewById(R.id.view);


        AtmosphereClient client = ClientFactory.getDefault().newClient(AtmosphereClient.class);

        RequestBuilder request = client.newRequestBuilder()
                .method(Request.METHOD.GET)
                .uri(serverIp)
                .trackMessageLength(true)
                .encoder(new Encoder<State, String>() {
                    @Override
                    public String encode(State data) {
                        try {
                            return mapper.writeValueAsString(data);
                        } catch (IOException e) {
                            throw new RuntimeException(e);
                        }
                    }
                })
                .decoder(new Decoder<String, State>() {
                    @Override
                    public State decode(Event type, String data) {

                        data = data.trim();

                        // Padding
                        if (data.length() == 0) {
                            return null;
                        }

                        if (type.equals(Event.MESSAGE)) {
                            try {
                                return mapper.readValue(data, State.class);
                            } catch (IOException e) {
                                e.printStackTrace();
                                return null;
                            }
                        } else {
                            return null;
                        }
                    }
                })
                .transport(Request.TRANSPORT.LONG_POLLING);

        final Socket socket = client.create();
    try {
        socket.on("message", new Function<State>() {
            @Override
            public void on(final State t) {
                uiHandler.post(new Runnable() {
                    @Override
                    public void run() {

                        view.append("State " + t.getState());
                    }
                });
            }
        }).on(new Function<Throwable>() {

            @Override
            public void on(Throwable t) {
                view.setText("ERROR 3: " + t.getMessage());
                t.printStackTrace();
            }

        }).open(request.build());
    } catch (IOException e) {
        e.printStackTrace();
    }

    act.setOnClickListener(new View.OnClickListener() {



            public void onClick(View v) {
                try {

                    socket.fire(new State("ON"));

                    Log.d("Client", "Client sent message");
                } catch (Throwable e) {
                    view.setText("ERROR 3: " + e.getMessage());
                    e.printStackTrace();
                }
            }
        });


}



}

I have added permmissions for internet and access network state.

added the depenency wasync-2.0.0-all from Maven Central.

But the connection is not success. the error i get is:

Caused by: java.lang.ClassNotFoundException: Didn't find class "sun.security.util.HostnameChecker" on path: DexPathList[[zip file "/data/app/com.att_lnx_admin.atmosphereclient-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.att_lnx_admin.atmosphereclient-1, /system/lib]]

somebody please help me with this.

Looks like your server side is not up-to-date. Try to use previous version on Android side: compile 'org.atmosphere:wasync:1.4.3'