Bonjour implementation on Android

Question

I am trying to implement bonjour/zero conf on my android app. I am using jmDns library for searching the all the available devices. Here is the code that I am using for searching the devices in the same network:

public class ListDevices extends ListActivity {
    JmDNS jmdns;
    JmDNSImpl impl;
    MulticastLock lock;
    protected ServiceListener listener;
    protected ServiceInfo info;
    public ListView lv;
    public ArrayList<String> deviceList;
    public int cancel = 0;
    public final static String TAG = "ListDevices";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        deviceList = new ArrayList<String>();
        showAllPrinters();

        setListAdapter(new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, deviceList));

        lv = getListView();
        lv.setTextFilterEnabled(true);

        lv.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                // When clicked, show a toast with the TextView text
                Toast.makeText(getApplicationContext(),
                       ((TextView) view).getText(), Toast.LENGTH_SHORT).show();
            }
        });
        this.listener = new ServiceListener() {
            public void serviceAdded(ServiceEvent event) {
                deviceList.add("Service added   : " + event.getName() + "."
                        + event.getType());
                Log.v(TAG, "Service added   : " + event.getName() + "."
                        + event.getType());
            }

            public void serviceRemoved(ServiceEvent event) {
                deviceList.add("Service removed : " + event.getName() + "."
                        + event.getType());
                Log.v(TAG, "Service removed : " + event.getName() + "."
                        + event.getType());
            }

            public void serviceResolved(ServiceEvent event) {
                deviceList.add("Service resolved: " + event.getInfo());
                Log.v(TAG, "Service resolved: " + event.getInfo());
            }
        };
    }

    public void showAllPrinters() {
        Log.d("ListDevices", "in showAllPrinters");
        try {

            WifiManager wifi = (WifiManager)
                               getSystemService(Context.WIFI_SERVICE);
            lock = wifi.createMulticastLock("fliing_lock");
            lock.setReferenceCounted(true);
            lock.acquire();

            InetAddress inetAddress = getLocalIpAddress();
            jmdns = JmDNS.create(inetAddress, "TEST");

            ServiceInfo[] infos = jmdns.list("_http._tcp.local.");

            if (infos != null && infos.length > 0) {
                for (int i = 0; i < infos.length; i++) {
                    deviceList.add(infos[i].getName());
                }
            } else {
                deviceList.add("No device found.");
            }
            impl = (JmDNSImpl) jmdns;

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public InetAddress getLocalIpAddress() {
        try {
            for (Enumeration<NetworkInterface> en = NetworkInterface
                    .getNetworkInterfaces(); en.hasMoreElements();) {
                NetworkInterface intf = (NetworkInterface) en.nextElement();
                for (Enumeration<InetAddress> enumIpAddr = intf
                        .getInetAddresses(); enumIpAddr.hasMoreElements();) {
                    InetAddress inetAddress = (InetAddress) enumIpAddr
                            .nextElement();
                    if (!inetAddress.isLoopbackAddress()) {
                        return inetAddress;
                    }
                }
            }
        } catch (SocketException ex) {
            Log.e("ListDevices", ex.toString());
        }
        return null;
    }

    @Override
    protected void onPause() {
        super.onPause();
        if (isFinishing()) {
            lock.release();
        }
    }
}

Basically, I am adding them in a list so that I can display a list of all available devices. Now when I am running this code, I am getting no exception/nothing like error. But on the other hand, nothing is added to my list [PS: there atleast 5-6 PCs and Macs are there in the network.

I also tried to get the list from this code:

jmdns.addServiceListener("_http._tcp.local.", listener);

listener is defined in the onCreate of the activity. But this also did not returned any device.

Please help, suggest what I am doing wrong here. Any help is appreciated!

Answer 1

Android 4.1 adds Network Service Discovery that seems to be just wrapping up the Bonjour stack in different terms. I also see a lower-level API called android.net.wifi.p2p.WifiP2pManager that exposes DNS-SD (as well as UPnP?) directly.

Note that the underlying mDNSResponder daemon does not seem to be running all the time, and is not used for systemwide DNS lookups (e.g. from a browser) as far as I can tell right now.