code: /*
   * Copyright 2014 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.physical_web.physicalweb;
  
  import org.physical_web.physicalweb.ssdp.Ssdp;
  import org.physical_web.physicalweb.ssdp.SsdpMessage;
  
  import android.content.Context;
  
  import java.io.IOException;
  
  /**
   * This class discovers Physical Web URI/URLs over SSDP.
   */
  public class SsdpUrlDeviceDiscoverer extends UrlDeviceDiscoverer implements Ssdp.SsdpCallback {
    private static final String TAG = SsdpUrlDeviceDiscoverer.class.getSimpleName();
    private static final String PHYSICAL_WEB_SSDP_TYPE = "urn:physical-web-org:device:Basic:1";
    private Context mContext;
    private Thread mThread;
    private Ssdp mSsdp;
  
    public SsdpUrlDeviceDiscoverer(Context context) {
      mContext = context;
    }
  
    public void startScanImpl() {
      new Thread(new Runnable() {
        @Override
        public void run() {
          try {
            // TODO(?): set timeout using getSsdp().start(NearbyBeaconsFragment.SCAN_TIME_MILLIS)
            // to ensure that SSDP scan thread is stopped automatically after timeout.
            // In this case there is no need to call stop().
            getSsdp().start(null);
            Thread.sleep(200);
            getSsdp().search(PHYSICAL_WEB_SSDP_TYPE);
          } catch (Exception e) {
            Log.e(TAG, e.getMessage(), e);
          }
        }
      }).start();
    }
  
    public void stopScanImpl() {
      new Thread(new Runnable() {
        @Override
        public void run() {
          try {
            getSsdp().stop();
          } catch (IOException e) {
            Log.e(TAG, e.getMessage(), e);
          }
        }
      }).start();
    }
  
    public synchronized Ssdp getSsdp() throws IOException {
      if (mSsdp == null) {
        mSsdp = new Ssdp(this);
      }
      return mSsdp;
    }
  
    @Override
    public void onSsdpMessageReceived(SsdpMessage ssdpMessage) {
      final String url = ssdpMessage.get("LOCATION");
      final String st = ssdpMessage.get("ST");
      if (url != null && PHYSICAL_WEB_SSDP_TYPE.equals(st)) {
        Log.d(TAG, "SSDP url received: " + url);
        new Thread(new Runnable() {
          @Override
          public void run() {
            reportUrlDevice(createUrlDeviceBuilder(TAG + url, url)
                .setDeviceType(Utils.SSDP_DEVICE_TYPE)
                .build());
          }
        }).start();
      }
    }
  }
  