diff --git a/service-t/src/com/android/server/NsdService.java b/service-t/src/com/android/server/NsdService.java
index ce105ce..b361720 100644
--- a/service-t/src/com/android/server/NsdService.java
+++ b/service-t/src/com/android/server/NsdService.java
@@ -83,6 +83,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -412,6 +413,13 @@
                                     clientId, NsdManager.FAILURE_OPERATION_NOT_RUNNING);
                         }
                         break;
+                    case NsdManager.REGISTER_SERVICE_CALLBACK:
+                        cInfo = getClientInfoForReply(msg);
+                        if (cInfo != null) {
+                            cInfo.onServiceInfoCallbackRegistrationFailed(
+                                    clientId, NsdManager.FAILURE_BAD_PARAMETERS);
+                        }
+                        break;
                     case NsdManager.DAEMON_CLEANUP:
                         maybeStopDaemon();
                         break;
@@ -490,6 +498,11 @@
                 maybeStopMonitoringSocketsIfNoActiveRequest();
             }
 
+            private void clearRegisteredServiceInfo(ClientInfo clientInfo) {
+                clientInfo.mRegisteredService = null;
+                clientInfo.mClientIdForServiceUpdates = 0;
+            }
+
             /**
              * Check the given service type is valid and construct it to a service type
              * which can use for discovery / resolution service.
@@ -793,6 +806,56 @@
                         clientInfo.mResolvedService = null;
                         // TODO: Implement the stop resolution with MdnsDiscoveryManager.
                         break;
+                    case NsdManager.REGISTER_SERVICE_CALLBACK:
+                        if (DBG) Log.d(TAG, "Register a service callback");
+                        args = (ListenerArgs) msg.obj;
+                        clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in callback registration");
+                            break;
+                        }
+
+                        if (clientInfo.mRegisteredService != null) {
+                            clientInfo.onServiceInfoCallbackRegistrationFailed(
+                                    clientId, NsdManager.FAILURE_ALREADY_ACTIVE);
+                            break;
+                        }
+
+                        maybeStartDaemon();
+                        id = getUniqueId();
+                        if (resolveService(id, args.serviceInfo)) {
+                            clientInfo.mRegisteredService = new NsdServiceInfo();
+                            clientInfo.mClientIdForServiceUpdates = clientId;
+                            storeRequestMap(clientId, id, clientInfo, msg.what);
+                        } else {
+                            clientInfo.onServiceInfoCallbackRegistrationFailed(
+                                    clientId, NsdManager.FAILURE_BAD_PARAMETERS);
+                        }
+                        break;
+                    case NsdManager.UNREGISTER_SERVICE_CALLBACK:
+                        if (DBG) Log.d(TAG, "Unregister a service callback");
+                        args = (ListenerArgs) msg.obj;
+                        clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in callback unregistration");
+                            break;
+                        }
+
+                        id = clientInfo.mClientIds.get(clientId);
+                        removeRequestMap(clientId, id, clientInfo);
+                        if (stopResolveService(id)) {
+                            clientInfo.onServiceInfoCallbackUnregistered(clientId);
+                        } else {
+                            Log.e(TAG, "Failed to unregister service info callback");
+                        }
+                        clearRegisteredServiceInfo(clientInfo);
+                        break;
                     case MDNS_SERVICE_EVENT:
                         if (!handleMDnsServiceEvent(msg.arg1, msg.arg2, msg.obj)) {
                             return NOT_HANDLED;
@@ -809,6 +872,19 @@
                 return HANDLED;
             }
 
+            private void notifyResolveFailedResult(boolean isListenedToUpdates, int clientId,
+                    ClientInfo clientInfo, int error) {
+                if (isListenedToUpdates) {
+                    clientInfo.onServiceInfoCallbackRegistrationFailed(clientId, error);
+                    clearRegisteredServiceInfo(clientInfo);
+                } else {
+                    // The resolve API always returned FAILURE_INTERNAL_ERROR on error; keep it
+                    // for backwards compatibility.
+                    clientInfo.onResolveServiceFailed(clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                    clientInfo.mResolvedService = null;
+                }
+            }
+
             private boolean handleMDnsServiceEvent(int code, int id, Object obj) {
                 NsdServiceInfo servInfo;
                 ClientInfo clientInfo = mIdToClientInfoMap.get(id);
@@ -859,6 +935,8 @@
                         // found services on the same interface index and their network at the time
                         setServiceNetworkForCallback(servInfo, lostNetId, info.interfaceIdx);
                         clientInfo.onServiceLost(clientId, servInfo);
+                        // TODO: also support registered service lost when not discovering
+                        clientInfo.maybeNotifyRegisteredServiceLost(servInfo);
                         break;
                     }
                     case IMDnsEventListener.SERVICE_DISCOVERY_FAILED:
@@ -895,10 +973,15 @@
                         String rest = fullName.substring(index);
                         String type = rest.replace(".local.", "");
 
-                        clientInfo.mResolvedService.setServiceName(name);
-                        clientInfo.mResolvedService.setServiceType(type);
-                        clientInfo.mResolvedService.setPort(info.port);
-                        clientInfo.mResolvedService.setTxtRecords(info.txtRecord);
+                        final boolean isListenedToUpdates =
+                                clientId == clientInfo.mClientIdForServiceUpdates;
+                        final NsdServiceInfo serviceInfo = isListenedToUpdates
+                                ? clientInfo.mRegisteredService : clientInfo.mResolvedService;
+
+                        serviceInfo.setServiceName(name);
+                        serviceInfo.setServiceType(type);
+                        serviceInfo.setPort(info.port);
+                        serviceInfo.setTxtRecords(info.txtRecord);
                         // Network will be added after SERVICE_GET_ADDR_SUCCESS
 
                         stopResolveService(id);
@@ -908,9 +991,8 @@
                         if (getAddrInfo(id2, info.hostname, info.interfaceIdx)) {
                             storeRequestMap(clientId, id2, clientInfo, NsdManager.RESOLVE_SERVICE);
                         } else {
-                            clientInfo.onResolveServiceFailed(
-                                    clientId, NsdManager.FAILURE_INTERNAL_ERROR);
-                            clientInfo.mResolvedService = null;
+                            notifyResolveFailedResult(isListenedToUpdates, clientId, clientInfo,
+                                    NsdManager.FAILURE_BAD_PARAMETERS);
                         }
                         break;
                     }
@@ -918,17 +1000,17 @@
                         /* NNN resolveId errorCode */
                         stopResolveService(id);
                         removeRequestMap(clientId, id, clientInfo);
-                        clientInfo.mResolvedService = null;
-                        clientInfo.onResolveServiceFailed(
-                                clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                        notifyResolveFailedResult(
+                                clientId == clientInfo.mClientIdForServiceUpdates,
+                                clientId, clientInfo, NsdManager.FAILURE_BAD_PARAMETERS);
                         break;
                     case IMDnsEventListener.SERVICE_GET_ADDR_FAILED:
                         /* NNN resolveId errorCode */
                         stopGetAddrInfo(id);
                         removeRequestMap(clientId, id, clientInfo);
-                        clientInfo.mResolvedService = null;
-                        clientInfo.onResolveServiceFailed(
-                                clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                        notifyResolveFailedResult(
+                                clientId == clientInfo.mClientIdForServiceUpdates,
+                                clientId, clientInfo, NsdManager.FAILURE_BAD_PARAMETERS);
                         break;
                     case IMDnsEventListener.SERVICE_GET_ADDR_SUCCESS: {
                         /* NNN resolveId hostname ttl addr interfaceIdx netId */
@@ -945,19 +1027,38 @@
                         // If the resolved service is on an interface without a network, consider it
                         // as a failure: it would not be usable by apps as they would need
                         // privileged permissions.
-                        if (netId != NETID_UNSET && serviceHost != null) {
-                            clientInfo.mResolvedService.setHost(serviceHost);
-                            setServiceNetworkForCallback(clientInfo.mResolvedService,
-                                    netId, info.interfaceIdx);
-                            clientInfo.onResolveServiceSucceeded(
-                                    clientId, clientInfo.mResolvedService);
+                        if (clientId == clientInfo.mClientIdForServiceUpdates) {
+                            if (netId != NETID_UNSET && serviceHost != null) {
+                                setServiceNetworkForCallback(clientInfo.mRegisteredService,
+                                        netId, info.interfaceIdx);
+                                final List<InetAddress> addresses =
+                                        clientInfo.mRegisteredService.getHostAddresses();
+                                addresses.add(serviceHost);
+                                clientInfo.mRegisteredService.setHostAddresses(addresses);
+                                clientInfo.onServiceUpdated(
+                                        clientId, clientInfo.mRegisteredService);
+                            } else {
+                                stopGetAddrInfo(id);
+                                removeRequestMap(clientId, id, clientInfo);
+                                clearRegisteredServiceInfo(clientInfo);
+                                clientInfo.onServiceInfoCallbackRegistrationFailed(
+                                        clientId, NsdManager.FAILURE_BAD_PARAMETERS);
+                            }
                         } else {
-                            clientInfo.onResolveServiceFailed(
-                                    clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                            if (netId != NETID_UNSET && serviceHost != null) {
+                                clientInfo.mResolvedService.setHost(serviceHost);
+                                setServiceNetworkForCallback(clientInfo.mResolvedService,
+                                        netId, info.interfaceIdx);
+                                clientInfo.onResolveServiceSucceeded(
+                                        clientId, clientInfo.mResolvedService);
+                            } else {
+                                clientInfo.onResolveServiceFailed(
+                                        clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                            }
+                            stopGetAddrInfo(id);
+                            removeRequestMap(clientId, id, clientInfo);
+                            clientInfo.mResolvedService = null;
                         }
-                        stopGetAddrInfo(id);
-                        removeRequestMap(clientId, id, clientInfo);
-                        clientInfo.mResolvedService = null;
                         break;
                     }
                     default:
@@ -1343,6 +1444,20 @@
         }
 
         @Override
+        public void registerServiceInfoCallback(int listenerKey, NsdServiceInfo serviceInfo) {
+            mNsdStateMachine.sendMessage(mNsdStateMachine.obtainMessage(
+                    NsdManager.REGISTER_SERVICE_CALLBACK, 0, listenerKey,
+                    new ListenerArgs(this, serviceInfo)));
+        }
+
+        @Override
+        public void unregisterServiceInfoCallback(int listenerKey) {
+            mNsdStateMachine.sendMessage(mNsdStateMachine.obtainMessage(
+                    NsdManager.UNREGISTER_SERVICE_CALLBACK, 0, listenerKey,
+                    new ListenerArgs(this, null)));
+        }
+
+        @Override
         public void startDaemon() {
             mNsdStateMachine.sendMessage(mNsdStateMachine.obtainMessage(
                     NsdManager.DAEMON_STARTUP, new ListenerArgs(this, null)));
@@ -1503,6 +1618,11 @@
         // The target SDK of this client < Build.VERSION_CODES.S
         private boolean mIsLegacy = false;
 
+        /*** The service that is registered to listen to its updates */
+        private NsdServiceInfo mRegisteredService;
+        /*** The client id that listen to updates */
+        private int mClientIdForServiceUpdates;
+
         private ClientInfo(INsdManagerCallback cb) {
             mCb = cb;
             if (DBG) Log.d(TAG, "New client");
@@ -1584,6 +1704,18 @@
             return mClientIds.keyAt(idx);
         }
 
+        private void maybeNotifyRegisteredServiceLost(@NonNull NsdServiceInfo info) {
+            if (mRegisteredService == null) return;
+            if (!Objects.equals(mRegisteredService.getServiceName(), info.getServiceName())) return;
+            // Resolved services have a leading dot appended at the beginning of their type, but in
+            // discovered info it's at the end
+            if (!Objects.equals(
+                    mRegisteredService.getServiceType() + ".", "." + info.getServiceType())) {
+                return;
+            }
+            onServiceUpdatedLost(mClientIdForServiceUpdates);
+        }
+
         void onDiscoverServicesStarted(int listenerKey, NsdServiceInfo info) {
             try {
                 mCb.onDiscoverServicesStarted(listenerKey, info);
@@ -1695,5 +1827,37 @@
                 Log.e(TAG, "Error calling onStopResolutionSucceeded", e);
             }
         }
+
+        void onServiceInfoCallbackRegistrationFailed(int listenerKey, int error) {
+            try {
+                mCb.onServiceInfoCallbackRegistrationFailed(listenerKey, error);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceInfoCallbackRegistrationFailed", e);
+            }
+        }
+
+        void onServiceUpdated(int listenerKey, NsdServiceInfo info) {
+            try {
+                mCb.onServiceUpdated(listenerKey, info);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceUpdated", e);
+            }
+        }
+
+        void onServiceUpdatedLost(int listenerKey) {
+            try {
+                mCb.onServiceUpdatedLost(listenerKey);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceUpdatedLost", e);
+            }
+        }
+
+        void onServiceInfoCallbackUnregistered(int listenerKey) {
+            try {
+                mCb.onServiceInfoCallbackUnregistered(listenerKey);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceInfoCallbackUnregistered", e);
+            }
+        }
     }
 }