public class EchoWebSocketListener extends WebSocketListener {
  @Override public void onOpen(WebSocket webSocket, Response response) {
    // called when the connection is opened
  }

  @Override public void onMessage(WebSocket webSocket, String text) {
    //...
  }

  @Override public void onMessage(WebSocket webSocket, ByteString bytes) {
    //...
  }

  @Override public void onClosing(WebSocket webSocket, int code, String reason){
    //...
  }

  @Override public void onFailure(WebSocket webSocket, Throwable t, Response response){
    //...
  }
}

@Override protected onCreate(Bundle savedInstance){
  OkHttpClient client = new OkHttpClient.Builder().build();

  Request request = new Request.Builder().url("ws://echo.websocket.org").build();
  EchoWebSocketListener listener = new EchoWebSocketListener();
  WebSocket ws = client.newWebSocket(request, listener);

  client.dispatcher().executorService().shutdown();
}