Android 6.0 NSD service bug

In the documentation it says:

NsdManager.DiscoveryListener: The listener notifies of a successful discovery and is used to stop discovery on this serviceType through a call on stopServiceDiscovery(NsdManager.DiscoveryListener). Cannot be null. Cannot be in use for an active service discovery.

The problem seems to be a century old of your listener. Probably the mDiscoveryListenerone you pass is already in use. Try creating a Listener by implementing DiscoveryListenerwhat you urge and save to discoverServices.

public class MiDiscoveryListener implements DiscoveryListener{
    //...
}

and create it at the moment when you start discovering services.

public void discoverServices() {
    // Solamente tratemos de descubrir servicios si todavía no lo estamos haciendo
    if (null==mDiscoveryListener)
        mDiscoveryListener = new MiDiscoveryListener();
        mNsdManager.discoverServices(SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, mDiscoveryListener);
    }
}

The application should call stopServiceDiscovery(NsdManager.DiscoveryListener) when discovery of this service type is no longer required, and/or whenever the application is paused or stopped.

onStop(){
    super.onStop();
    if (null!=mDiscoveryListener){
        mNsdManager.stopDiscovery(mDiscoveryListener);
        mDiscoveryListener=null;
    }
}

You're probably going to have to design a bit more precisely the life cycles of your activities and when service discovery starts.

The real problem in this example on NSD is:

Caused by: java.lang.IllegalArgumentException: listener already in use

What you have to ensure is not to use the same defined listener, for this you can create a class to not use the same listener instance:

//mNsdManager.resolveService(service, mResolveListener); //Incorrecto.
mNsdManager.resolveService(service, new MyResolveListener());

The class in question would be:

private class MyResolveListener implements NsdManager.ResolveListener {
    @Override
    public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
        Log.e(TAG, "*Jorgesys Resolve failed" + errorCode);
    }

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

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

I add the complete NsdHelper class:

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * 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.example.android.nsdchat;

import android.content.Context;
import android.net.nsd.NsdServiceInfo;
import android.net.nsd.NsdManager;
import android.util.Log;

public class NsdHelper {

    Context mContext;

    NsdManager mNsdManager;
    NsdManager.ResolveListener mResolveListener;
    NsdManager.DiscoveryListener mDiscoveryListener;
    NsdManager.RegistrationListener mRegistrationListener;

    public static final String SERVICE_TYPE = "_http._tcp.";

    public static final String TAG = "NsdHelper";
    public String mServiceName = "NsdChat";

    NsdServiceInfo mService;

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

    public void initializeNsd() {
        //initializeResolveListener();
        //initializeDiscoveryListener();
        //initializeRegistrationListener();
        //mNsdManager.init(mContext.getMainLooper(), this);
    }

    public void registerService(int port) {
        NsdServiceInfo serviceInfo  = new NsdServiceInfo();
        serviceInfo.setPort(port);
        serviceInfo.setServiceName(mServiceName);
        serviceInfo.setServiceType(SERVICE_TYPE);
        mRegistrationListener = new MyRegistrationListener(); //Jorgesys
        mNsdManager.registerService(
                serviceInfo, NsdManager.PROTOCOL_DNS_SD, mRegistrationListener);

    }

    public void discoverServices() {
        mDiscoveryListener = new MyDiscoveryListener(); //Jorgesys
        mNsdManager.discoverServices(
                SERVICE_TYPE, NsdManager.PROTOCOL_DNS_SD, mDiscoveryListener);
    }

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

    public NsdServiceInfo getChosenServiceInfo() {
        return mService;
    }

    public void tearDown() {
        mNsdManager.unregisterService(mRegistrationListener);
    }

    /*** New classes to avoid : java.lang.IllegalArgumentException: listener already in use ***/

    private class MyResolveListener implements NsdManager.ResolveListener {
        @Override
        public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
            Log.e(TAG, "*Jorgesys Resolve failed" + errorCode);
        }

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

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

    //mDiscoveryListener = new NsdManager.DiscoveryListener() {

    private class MyRegistrationListener implements NsdManager.RegistrationListener {

        @Override
        public void onServiceRegistered(NsdServiceInfo NsdServiceInfo) {
            mServiceName = NsdServiceInfo.getServiceName();
        }

        @Override
        public void onRegistrationFailed(NsdServiceInfo arg0, int arg1) {
        }

        @Override
        public void onServiceUnregistered(NsdServiceInfo arg0) {
        }

        @Override
        public void onUnregistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
        }
    }

    private class MyDiscoveryListener implements 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" + 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)){
                mNsdManager.resolveService(service, new MyResolveListener());
            }
        }

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

    }
}