Unable to register NSD Service

Issue

I am trying to work with NSD and I find myself stuck at the very begining..

I set up a very basic layout with a single big button. This button's purpose is to start and register a service on my device so other devices would be able to connect to it through LAN. One press of the said button calls the folowing method in my only Activity :

public void startService(View view){
    initSocket();
    initRegList();
    regService();
}

Following the DevBytes: Network Service Discovery video, I implemented the methods called above, like so (pardon my YOLO-ing for debugging purposes) :

public void initSocket(){

try {
 mSocket = new ServerSocket(0);
} catch (IOException e) {
 e.printStackTrace();
}
 mPort = mSocket.getLocalPort();
 Log.e("YOLO-PORT", String.valueOf(mPort));
}

public void regService(){

    NsdServiceInfo serviceInfo = new NsdServiceInfo();
    serviceInfo.setServiceName("MyCoolService");
    serviceInfo.setServiceType("_myapp.tcp.");
    serviceInfo.setPort(mPort);
    mNsdman = (NsdManager) this.getSystemService(this.NSD_SERVICE);
    mNsdman.registerService(serviceInfo,NsdManager.PROTOCOL_DNS_SD,mReglist);
}

public void initRegList() {

    mReglist = new NsdManager.RegistrationListener() {
        @Override
        public void onRegistrationFailed(NsdServiceInfo nsdServiceInfo, int i) {
            Log.e("YOLO-FAIL", "REG_FAIL, errcode = " + String.valueOf(i));
        }

        @Override
        public void onUnregistrationFailed(NsdServiceInfo nsdServiceInfo, int i) {
            Log.e("YOLO-FAIL", "UNREG_FAIL, errcode = " + String.valueOf(i));
        }

        @Override
        public void onServiceRegistered(NsdServiceInfo nsdServiceInfo) {
            mServName = nsdServiceInfo.getServiceName();
            Log.e("YOLO-NAME", mServName);
        }

        @Override
        public void onServiceUnregistered(NsdServiceInfo nsdServiceInfo) {
            Log.e("YOLO-OK", "UNREG");
        }
    };

}

My problem is I keep falling into onUnregistrationFailed method of the listener with a return code = 0.

Below you will find Logcat entries apearing when I press the said button :

09-14 21:54:03.904  18672-18672/fr.lpnsk.lollibox E/YOLO-PORT﹕ 48321
09-14 21:54:04.124      180-531/? E/MDnsDS﹕ service register request 22 got an error from DNSServiceRegister -65540
09-14 21:54:04.125      538-607/? E/NsdService﹕ Failed to execute registerService com.android.server.NativeDaemonConnector$NativeDaemonArgumentException: command '76 mdnssd register 22 MyCoolService _myapp.tcp. 48321' failed with '501 76 serviceRegister request got an error from DNSServiceRegister'
09-14 21:54:04.126      180-531/? E/MDnsDS﹕ register stop used unknown requestId 22
09-14 21:54:04.126      538-607/? E/NsdService﹕ Failed to execute unregisterService com.android.server.NativeDaemonConnector$NativeDaemonArgumentException: command '77 mdnssd stop-register 22' failed with '501 77 Unknown requestId'
09-14 21:54:04.127  18672-19953/fr.lpnsk.lollibox E/YOLO-FAIL﹕ REG_FAIL, errcode = 0

Am I missing something obvious here ?

Thank you for your help !

Solution

Am I missing something obvious here?

Yes. You missed the underscore _ sign before tcp when setting the service type. It should be:

serviceInfo.setServiceType("_myapp._tcp.");

From the official documentation:

...the service type specifies which protocol and transport layer the application uses. The syntax is "_protocol._transportlayer".

Answered By - Onik