DiscoveringThread.java

/**
 * Copyright 2010 Eric Taix
 * 
 * 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 com.bigpupdev.synodroid.wizard;

import java.io.IOException;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;

import javax.jmdns.JmDNS;
import javax.jmdns.ServiceInfo;

import com.bigpupdev.synodroid.Synodroid;

import android.content.Context;
import android.net.wifi.WifiManager;
import android.net.wifi.WifiManager.MulticastLock;
import android.os.Message;
import android.util.Log;

/**
 * A thread which try to discover NAS on the local network (use the ZeroConf protocol).
 * 
 * @author Eric Taix (eric.taix at gmail.com)
 */
public class DiscoveringThread extends Thread {

	// The current context in which this thread is running
	private Context context;
	// The message handler
	private AddHandler handler;
	private boolean DEBUG;

	/**
	 * The constructor
	 * 
	 * @param ctxP
	 * @param hdlP
	 */
	public DiscoveringThread(Context ctxP, AddHandler hdlP, boolean debug) {
		context = ctxP;
		handler = hdlP;
		DEBUG = debug;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see java.lang.Thread#run()
	 */
	@Override
	public void run() {
		JmDNS jmdns = null;
		WifiManager wifi = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
		MulticastLock lock = wifi.createMulticastLock("fliing_lock");
		lock.setReferenceCounted(true);
		try {
			lock.acquire();
			InetAddress addr = getLocalIpAddress(DEBUG);
			jmdns = JmDNS.create(addr);
			ServiceInfo[] infos = jmdns.list("_http._tcp.local.");
			Message msg = new Message();
			msg.what = AddHandler.MSG_SERVER_FOUND;
			msg.obj = infos;
			handler.sendMessage(msg);
		} catch (IllegalArgumentException iae){ 
			// JMDNS failed parsing the results it received. Fake no server found...
			ServiceInfo[] infos = new ServiceInfo[0];
			Message msg = new Message();
			msg.what = AddHandler.MSG_SERVER_FOUND;
			msg.obj = infos;
			handler.sendMessage(msg);
			if (DEBUG) {
				Log.e(Synodroid.DS_TAG, "Failed parsing JMDNS results.");
				Log.e(Synodroid.DS_TAG, iae.toString());
			}
		} catch (SecurityException se) {
			// Could not acquire lock. Fake no server found...
			ServiceInfo[] infos = new ServiceInfo[0];
			Message msg = new Message();
			msg.what = AddHandler.MSG_SERVER_FOUND;
			msg.obj = infos;
			handler.sendMessage(msg);
			if (DEBUG) {
				Log.e(Synodroid.DS_TAG, "Could not acquire networking lock.");
				Log.e(Synodroid.DS_TAG, se.toString());
			}
		} catch (IOException e) {
			// Networking exception caught. Fake no server found...
			ServiceInfo[] infos = new ServiceInfo[0];
			Message msg = new Message();
			msg.what = AddHandler.MSG_SERVER_FOUND;
			msg.obj = infos;
			handler.sendMessage(msg);
			if (DEBUG) {
				Log.e(Synodroid.DS_TAG, "Networking exception caught.");
				Log.e(Synodroid.DS_TAG, e.toString()); 
			}
		} finally {
			if (jmdns != null)
				jmdns.close();
			if (lock != null) {
				if (lock.isHeld())
					lock.release();
			}
		}
	}

	/**
	 * Return local IP adress. This method iterates to each network interface and try to find something different that loopback address
	 * 
	 * @return
	 */
	private static InetAddress getLocalIpAddress(boolean debug) {
		try {
			for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
				NetworkInterface intf = en.nextElement();
				
				for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
					InetAddress inetAddress = enumIpAddr.nextElement();
					if (inetAddress instanceof Inet4Address && !inetAddress.isLoopbackAddress()) {
						return inetAddress;
					}
				}
			}
		} catch (SocketException ex) {
			if (debug) Log.e(Synodroid.DS_TAG, ex.toString());
		}
		return null;
	}

}