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 running the code from https://github.com/joeluchoa/nsd using four galaxy nexus and most of the times each of them discoveries different number of services at the same time.

Basically I run a service with a ServerSocket:

ServerSocket server = new ServerSocket(0);
Log.i(TAG, "IP " + server.getInetAddress()
        + ", running on port " + server.getLocalPort());

Intent intent = new Intent(MySocket.this,
        MyPresence.class);
intent.putExtra("PORT", server.getLocalPort());
startService(intent);

Then I publish it using the method registerService from NsdManager:

NsdServiceInfo serviceInfo = new NsdServiceInfo();

serviceInfo.setServiceName(Build.SERIAL + "-" + new Date().getTime());
serviceInfo.setServiceType(SERVICE_TYPE);
serviceInfo.setPort(port);

mNsdManager.registerService(serviceInfo, NsdManager.PROTOCOL_DNS_SD,
        mRegistrationListener);

To discover the services I use the method discoverServices from NsdManager:

mNsdManager.discoverServices(SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD,
        mDiscoveryListener);

With mDiscoveryListener as follows:

mDiscoveryListener = new NsdManager.DiscoveryListener() {

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

    @Override
    public void onServiceFound(NsdServiceInfo service) {
        Log.d(TAG, "Service discovery success");
        Log.d(TAG, String.format("%s %s %s %d",
                service.getServiceName(), service.getServiceType(),
                service.getHost(), service.getPort()));
        if (!service.getServiceType().contains(SERVICE_TYPE)) {
            Log.d(TAG,
                    "Unknown Service Type: " + service.getServiceType());
        } else if (service.getServiceName().equals(mServiceName)) {
            Log.d(TAG, "Same machine: " + mServiceName);
        } else {
            mNsdManager.resolveService(service, mResolveListener);
        }
    }

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

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

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

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

Am i doing something wrong? Does anybody know a solution or a workaround for this?

Answer 1

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 2

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

Answer 3

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.