Android NSD not discovering all services

Question

I\'m trying to run an application using Android Native Service Discovery but sometimes when I run the application, it doesn\'t discover all services from my network. I\'m runnin

Answer 1

I tend to think the whole NSD implementation in Android must be a bit flaky. I also have a simple Activity just to demonstrate the lifecycle (no Sockets are opened), and sometimes it works, and sometimes it does not work. I simply don't get it. Here is the Activity if anybody has some insight:

https://github.com/mholzel/Dump/blob/master/NetworkServiceDiscoveryViaWifi.java

On the other hand, Wifi Direct based NSD seems to be very reliable for me:

https://github.com/mholzel/Dump/blob/master/NetworkServiceDiscoveryViaWifiDirect.java

Note that neither of these Activities have any resources, so just add the Activities to your Manifest with the proper permissions.

Answer 2

I was seeing the same issue with devices not being discovered and was able to fix it by acquiring the WifiManager Multicast lock prior to discovering services:

val multicastLock: WifiManager.MulticastLock = (mContext.getSystemService(Context.WIFI_SERVICE) as WifiManager).createMulticastLock(TAG)
multicastLock.setReferenceCounted(true)
    
multicastLock.acquire()
    
mNsdManager.discoverServices(SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, mDiscoveryListener)

And later releasing the lock when done discovering services:

mNsdManager.stopServiceDiscovery(mDiscoveryListener)
    
multicastLock.release()

Answer 3

To discover all services of the connected network just change the service type you are discovering,

public static final String SERVICE_TYPE = "_services._dns-sd._udp";

Answer 4

I had the same issue, reinstall helped. Try to use:)

Answer 5

It may be little late for the answer, but I found a good solution for NSD for android give on their developer site. I made a few modification and it works perfectly fine.

public class NsdClient {
private Context mContext;

private NsdManager mNsdManager;
NsdManager.DiscoveryListener mDiscoveryListener;

//To find all the available networks SERVICE_TYPE = "_services._dns-sd._udp"
public static final String SERVICE_TYPE = "_hap._tcp.";
public static final String TAG = "NsdClient";

private static ArrayList<NsdServiceInfo> ServicesAvailable = new ArrayList<>();

public NsdClient(Context context) {
    mContext = context;
    mNsdManager = (NsdManager) context.getSystemService(Context.NSD_SERVICE);
}

public void initializeNsd() {
    initializeDiscoveryListener();
}

public void initializeDiscoveryListener() {
    mDiscoveryListener = new NsdManager.DiscoveryListener() {

        @Override
        public void onDiscoveryStarted(String regType) {
            Log.d(TAG, "Service discovery started " + regType);
        }

        @Override
        public void onServiceFound(NsdServiceInfo service) {
            Log.d(TAG, "Service discovery success " + service);
            AVAILABLE_NETWORKS.add(service);

            if (!service.getServiceType().equals(SERVICE_TYPE)) {
                Log.d(TAG, "Unknown Service Type: " + service.getServiceType());
            } else if (service.getServiceName().equals(mServiceName)) {
                Log.d(TAG, "Same Machine: " + mServiceName);
            } else if (service.getServiceName().contains(mServiceName)) {
                Log.d(TAG, "Resolving Services: " + service);
                mNsdManager.resolveService(service, new initializeResolveListener());
            }
        }

        @Override
        public void onServiceLost(NsdServiceInfo service) {
            Log.e(TAG, "service lost" + service);
            if (ServicesAvailable.equals(service)) {
                ServicesAvailable = null;
            }
        }

        @Override
        public void onDiscoveryStopped(String serviceType) {
            Log.i(TAG, "Discovery stopped: " + serviceType);
        }

        @Override
        public void onStartDiscoveryFailed(String serviceType, int errorCode) {
            Log.e(TAG, "Discovery failed: Error code:" + errorCode);
            mNsdManager.stopServiceDiscovery(this);
        }

        @Override
        public void onStopDiscoveryFailed(String serviceType, int errorCode) {
            Log.e(TAG, "Discovery failed: Error code:" + errorCode);
            mNsdManager.stopServiceDiscovery(this);
        }
    };
}

public class initializeResolveListener implements NsdManager.ResolveListener {

    @Override
    public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
        Log.e(TAG, "Resolve failed " + errorCode);
        switch (errorCode) {
            case NsdManager.FAILURE_ALREADY_ACTIVE:
                Log.e(TAG, "FAILURE ALREADY ACTIVE");
                mNsdManager.resolveService(serviceInfo, new initializeResolveListener());
                break;
            case NsdManager.FAILURE_INTERNAL_ERROR:
                Log.e(TAG, "FAILURE_INTERNAL_ERROR");
                break;
            case NsdManager.FAILURE_MAX_LIMIT:
                Log.e(TAG, "FAILURE_MAX_LIMIT");
                break;
        }
    }

    @Override
    public void onServiceResolved(NsdServiceInfo serviceInfo) {
        Log.e(TAG, "Resolve Succeeded. " + serviceInfo);


        if (serviceInfo.getServiceName().equals(mServiceName)) {
            Log.d(TAG, "Same IP.");
            return;
        }

    }
}

public void stopDiscovery() {
    mNsdManager.stopServiceDiscovery(mDiscoveryListener);
}

public List<NsdServiceInfo> getChosenServiceInfo() {
    return ServicesAvailable;
}

public void discoverServices() {
    mNsdManager.discoverServices(
            SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, mDiscoveryListener);
}
}

Hope it this helps

Answer 6

I'm afraid that there are still bugs in the implementation that cause it to miss services. I've done a couple days of testing with multiple Android devices and a MacBook, and it just doesn't work all the time. I documented my findings on a bug report over in the Android bug tracker: https://code.google.com/p/android/issues/detail?id=178080