NsdManager

public final class NsdManager
extends Object

java.lang.Object
   ↳ android.net.nsd.NsdManager

Provides APIs for discovering and advertising network services on the local network.

Network Service Discovery (NSD) allows applications to find other devices on a local network that support the services the application is interested in. For example, a game can find other players on the same local network, or a document viewer can find printers.

The implementation is based on DNS Service Discovery (DNS-SD) as described in RFC 6763, and operates over Multicast DNS (mDNS).

SDK Extensions

The NsdManager API is updated via SDK extensions. This allows newer features and APIs to be available on devices running older versions of Android. Applications should generally use SDK extension version checks instead of SDK version (Build.VERSION) checks when interacting with NsdManager.

Usage Patterns

The API is asynchronous. Requests are made to the system, and results are returned through listener or callback interfaces.

Discovering and Tracking Services

The easiest way to find and maintain an up-to-date list of services is to use registerServiceInfoCallback(DiscoveryRequest,Executor,ServiceInfoCallback). This API, available starting from "T extensions 22" (which covers all Android 14+ devices), combines discovery and resolution into a single operation. It automatically notifies the app when a service is found, when its properties (like IP addresses or TXT records) change, and when it becomes unavailable.

On older devices, or if an app needs fine-grained control over which services to resolve, use overloads of discoverServices(DiscoveryRequest, Executor, DiscoveryListener) with a DiscoveryListener, then call registerServiceInfoCallback(NsdServiceInfo,Executor,ServiceInfoCallback) or resolveService(NsdServiceInfo, ResolveListener) for the specific services of interest.

Advertising Services

To make a service on the current device discoverable by others, use registerService(AdvertisingRequest, Executor, RegistrationListener). The app provides an NsdServiceInfo containing the service name, type, and port.

Wi-Fi Multicast Lock

Performing mDNS operations on Wi-Fi requires the device to receive multicast packets.

  • Before T extensions 7 (Android 12 and below devices, and Android 13 devices that have not received the T extensions 7 update): Apps must manually acquire a WifiManager.MulticastLock to receive mDNS packets, even when the app is in the foreground.
  • Starting from T extensions 7: The system automatically manages multicast reception for apps in the foreground. Background apps should still avoid taking the lock unless absolutely necessary to minimize battery impact.

Local network permission (Android 17+)

Starting with API 37, access to the local network is restricted.

Applications targeting API 37 or higher generally require the Manifest.permission.ACCESS_LOCAL_NETWORK permission to communicate with local devices. However, NsdManager provides a way to gain access to specific services without this broad permission:

  1. An app calls discoverServices(DiscoveryRequest, Executor, DiscoveryListener) or registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback) with the DiscoveryRequest.FLAG_SHOW_PICKER flag. This triggers a system-provided UI allowing the user to choose a specific service.
  2. Once the user selects a service, the app is granted permission to communicate with that specific device through NsdServiceInfo.getHostAddresses() on NsdServiceInfo.getNetwork(). The app can also receive updates for that service without requiring the ACCESS_LOCAL_NETWORK permission by calling registerServiceInfoCallback(NsdServiceInfo,Executor,ServiceInfoCallback). This grant persists across reboots.
  3. If the Network reconnects or the service changes addresses, apps must use registerServiceInfoCallback(NsdServiceInfo,Executor,ServiceInfoCallback) to obtain up-to-date IP addresses with the grant applied. Apps should avoid storing service IP addresses as they can change over time.
  4. Apps can use checkPermissionForService(String, String, Executor, IntConsumer) to verify if they still have access to a previously selected service.
  5. To rediscover previously approved services without showing the UI again, apps can use DiscoveryRequest.FLAG_USER_APPROVED_ONLY.

Example finding and resolving a single service

// Discover a service for a given service type, with an optional name filter. Consider
 // calling in a withTimeout block.
 suspend fun findService(serviceType: String, nameFilter: PatternMatcher?): NsdServiceInfo? {
     if (SdkExtensions.getExtensionVersion(Build.VERSION_CODES.TIRAMISU) < 22) {
         return findServiceLegacy(serviceType, nameFilter)
     }
     // Note the Wi-Fi multicast lock is not necessary for foreground discovery in recent SDKs
     // Using kotlinx-coroutines-core
     return suspendCancellableCoroutine { cont ->
         val request = DiscoveryRequest.Builder(serviceType)
             .setServiceNameFilter(nameFilter)
             .setFlags(DiscoveryRequest.FLAG_SHOW_PICKER)
             .build()

         val listener = object : NsdManager.ServiceInfoCallback {
             override fun onServiceUpdated(serviceInfo: NsdServiceInfo) {
                 if (cont.isActive) cont.resume(serviceInfo)
                 // With FLAG_SHOW_PICKER only the selected service is returned, the
                 // listener is then unregistered automatically
             }

             override fun onServiceInfoCallbackRegistrationFailed(errorCode: Int) {
                 cont.resumeWithException(DiscoveryException(errorCode))
             }

             override fun onServiceInfoCallbackUnregistered() {
                 // This will be called if the user dismisses the picker without selecting
                 if (cont.isActive) cont.resume(null)
             }
         }

         nsdManager.registerServiceInfoCallback(request, Runnable::run, listener)
         cont.invokeOnCancellation {
             // unregistration is safe to call multiple times on SDK Ext 22+
             nsdManager.unregisterServiceInfoCallback(listener)
         }
     }
 }

 private suspend fun findServiceLegacy(
     serviceType: String, nameFilter: PatternMatcher?): NsdServiceInfo? {
     val tiramisuExt = SdkExtensions.getExtensionVersion(Build.VERSION_CODES.TIRAMISU)
     val lock = if (tiramisuExt < 7) {
         getSystemService(WifiManager::class.java)
             .createMulticastLock("MyAppTag").apply { acquire() }
     } else {
         null
     }

     try {
         val discoveredService = suspendCancellableCoroutine { cont ->
             val discoveryListener = object : NsdManager.DiscoveryListener {
                 override fun onServiceFound(info: NsdServiceInfo) {
                     // onServiceFound may be called multiple times
                     if (!cont.isActive) return
                     // Apps implement their own logic to select which discovered service
                     // to use. They may show a UI selector to the user, or have some
                     // custom name filtering to identify the service as assumed here.
                     if (nameFilter?.match(info.serviceName) == false) return
                     try {
                         // This may throw IllegalArgumentException on older SDKs if
                         // discovery was stopped already
                         nsdManager.stopServiceDiscovery(this)
                     } catch (_: IllegalArgumentException) {}
                     cont.resume(info)
                 }
                 override fun onStartDiscoveryFailed(type: String, err: Int) {
                     cont.resumeWithException(DiscoveryException(err))
                 }
                 override fun onDiscoveryStarted(type: String) {}
                 override fun onDiscoveryStopped(type: String) {}
                 override fun onServiceLost(info: NsdServiceInfo) {}
                 override fun onStopDiscoveryFailed(type: String, err: Int) {}
             }
             nsdManager.discoverServices(
                 serviceType, NsdManager.PROTOCOL_DNS_SD, discoveryListener)
             cont.invokeOnCancellation {
                 try {
                     nsdManager.stopServiceDiscovery(discoveryListener)
                 } catch (_: IllegalArgumentException) {}
             }
         }

         return suspendCancellableCoroutine { cont ->
             val resolveListener = object : NsdManager.ResolveListener {
                 override fun onServiceResolved(info: NsdServiceInfo) {
                     cont.resume(info)
                 }
                 override fun onResolveFailed(info: NsdServiceInfo, err: Int) {
                     cont.resumeWithException(DiscoveryException(err))
                 }
             }
             nsdManager.resolveService(discoveredService, resolveListener)
             cont.invokeOnCancellation {
                 if (tiramisuExt >= 7) {
                     try {
                         nsdManager.stopServiceResolution(resolveListener)
                     } catch (_: IllegalArgumentException) {}
                 }
             }
         }
     } finally {
         lock?.release()
     }
 }

Example re-finding a previously discovered service

// Fetch the latest service information (such as IP addresses) for a service that was
 // previously discovered and saved in the app. This should typically be used before
 // each connection to the service to fetch up-to-date NsdServiceInfo#getHostAddresses()
 // and NsdServiceInfo#getNetwork(). Consider calling in a withTimeout block.
 suspend fun findKnownService(serviceType: String, serviceName: String): NsdServiceInfo? {
     if (SdkExtensions.getExtensionVersion(Build.VERSION_CODES.TIRAMISU) < 22) {
         return findKnownServiceLegacy(serviceType, serviceName)
     }
     val hasPermission = if (Build.VERSION.SDK_INT < Build.VERSION_CODES.CINNAMON_BUN) {
         true
     } else suspendCancellableCoroutine { cont ->
         nsdManager.checkPermissionForService(serviceName, serviceType, Runnable::run) {
             cont.resume(it == NsdManager.SERVICE_PERMISSION_GRANTED)
         }
     }
     if (!hasPermission) {
         // Trigger FLAG_SHOW_PICKER flow for the user to reselect the service
         return findService(serviceType,
             PatternMatcher(serviceName, PatternMatcher.PATTERN_LITERAL))
     }

     return suspendCancellableCoroutine { cont ->
         val listener = object : NsdManager.ServiceInfoCallback {
             override fun onServiceUpdated(serviceInfo: NsdServiceInfo) {
                 if (!cont.isActive) return // onServiceUpdated may be called multiple times
                 cont.resume(serviceInfo)
                 nsdManager.unregisterServiceInfoCallback(this)
             }

             override fun onServiceInfoCallbackRegistrationFailed(errorCode: Int) {
                 cont.resumeWithException(DiscoveryException(errorCode))
             }

             override fun onServiceInfoCallbackUnregistered() {}
         }

         val serviceToFind = NsdServiceInfo().apply {
             this.serviceName = serviceName
             this.serviceType = serviceType
             // Set to find on specific Networks, see ConnectivityManager#requestNetwork
             // this.network = network
         }
         nsdManager.registerServiceInfoCallback(
             serviceToFind, Runnable::run, listener)
         cont.invokeOnCancellation {
             nsdManager.unregisterServiceInfoCallback(listener)
         }
     }
 }

 private suspend fun findKnownServiceLegacy(
     serviceType: String, serviceName: String): NsdServiceInfo? {
     val tiramisuExt = SdkExtensions.getExtensionVersion(Build.VERSION_CODES.TIRAMISU)
     return suspendCancellableCoroutine { cont ->
         val lock = if (tiramisuExt < 7) {
             getSystemService(WifiManager::class.java)
                 .createMulticastLock("MyAppTag").apply { acquire() }
         } else {
             null
         }
         try {
             val listener = object : NsdManager.ResolveListener {
                 override fun onResolveFailed(serviceInfo: NsdServiceInfo, errorCode: Int) {
                     cont.resumeWithException(DiscoveryException(errorCode))
                 }

                 override fun onServiceResolved(serviceInfo: NsdServiceInfo) {
                     if (cont.isActive) cont.resume(serviceInfo)
                 }
             }
             val serviceToFind = NsdServiceInfo().apply {
                 this.serviceName = serviceName
                 this.serviceType = serviceType
             }
             nsdManager.resolveService(serviceToFind, listener)
             cont.invokeOnCancellation {
                 if (SdkExtensions.getExtensionVersion(Build.VERSION_CODES.TIRAMISU) >= 7) {
                     try {
                         nsdManager.stopServiceResolution(listener)
                     } catch (_: IllegalArgumentException) {
                     }
                 }
             }
         } finally {
             lock?.release()
         }
     }
 }

Example advertising a service

// Advertise a service for other devices to connect to the current device. This should be called
 // after opening a listening socket to handle connections from other devices, on a dynamic port
 // to avoid conflicts. Note this always requires the ACCESS_LOCAL_NETWORK permission.
 fun advertiseService(portNumber: Int): Pair<NsdManager.RegistrationListener, MulticastLock?> {
     // The Wi-Fi multicast lock is not necessary for advertising on Wi-Fi while in the
     // foreground since SDK extension 7
     val lock = if (SdkExtensions.getExtensionVersion(Build.VERSION_CODES.TIRAMISU) < 7) {
         getSystemService(WifiManager::class.java).createMulticastLock("MyAppTag").apply {
             acquire()
         }
     } else null

     val service = NsdServiceInfo().apply {
         serviceName = "My service name"
         serviceType = "_servicetype._tcp"
         port = portNumber
     }
     val listener = object : NsdManager.RegistrationListener {
         override fun onRegistrationFailed(serviceType: NsdServiceInfo, errorCode: Int) {}
         override fun onServiceRegistered(serviceInfo: NsdServiceInfo) {}
         override fun onUnregistrationFailed(serviceType: NsdServiceInfo, errorCode: Int) {}
         override fun onServiceUnregistered(serviceType: NsdServiceInfo) {}
     }
     nsdManager.registerService(service, NsdManager.PROTOCOL_DNS_SD, listener)
     return Pair(listener, lock)
 }

 fun stopAdvertisingService(listener: NsdManager.RegistrationListener, lock: MulticastLock?) {
     lock?.release()
     // unregisterService may throw IllegalArgumentException on T SDK extension < 22 if the
     // listener was already unregistered or failed to register
     try {
         nsdManager.unregisterService(listener)
     } catch (_: IllegalArgumentException) {}
 }

Summary

Nested classes

interface NsdManager.DiscoveryListener

Interface for callback invocation for service discovery 

interface NsdManager.RegistrationListener

Interface for callback invocation for service registration 

interface NsdManager.ResolveListener

Callback for use with NsdManager.resolveService to resolve the service info and use with NsdManager.stopServiceResolution to stop resolution. 

interface NsdManager.ServiceInfoCallback

Callback to listen to service info updates. 

Constants

String ACTION_NSD_STATE_CHANGED

Broadcast intent action to indicate whether network service discovery is enabled or disabled.

String EXTRA_NSD_STATE

The lookup key for an int that indicates whether network service discovery is enabled or disabled.

int FAILURE_ALREADY_ACTIVE

Indicates that the operation failed because it is already active.

int FAILURE_BAD_PARAMETERS

Indicates that the service has failed to resolve because of bad parameters.

int FAILURE_INTERNAL_ERROR

Failures are passed with RegistrationListener.onRegistrationFailed, RegistrationListener.onUnregistrationFailed, DiscoveryListener.onStartDiscoveryFailed, DiscoveryListener.onStopDiscoveryFailed or ResolveListener.onResolveFailed.

int FAILURE_MAX_LIMIT

Indicates that the operation failed because the maximum outstanding requests from the applications have reached.

int FAILURE_OPERATION_NOT_RUNNING

Indicates that the stop operation failed because it is not running.

int FAILURE_PERMISSION_DENIED

Indicates that the operation failed because the caller did not have the required permissions.

int NSD_STATE_DISABLED

Network service discovery is disabled

int NSD_STATE_ENABLED

Network service discovery is enabled

int PROTOCOL_DNS_SD

Dns based service discovery protocol

int SERVICE_PERMISSION_DENIED

Indicates the caller is not allowed to register service info callbacks or resolve a service.

int SERVICE_PERMISSION_GRANTED

Indicates the caller can register service info callbacks or resolve a service.

Public methods

void checkPermissionForService(String serviceName, String serviceType, Executor executor, IntConsumer resultReceiver)

Check whether the caller can register service info callbacks or resolve a service.

void discoverServices(String serviceType, int protocolType, NetworkRequest networkRequest, Executor executor, NsdManager.DiscoveryListener listener)

Initiate service discovery to browse for instances of a service type.

void discoverServices(DiscoveryRequest discoveryRequest, Executor executor, NsdManager.DiscoveryListener listener)

Initiates service discovery to browse for instances of a service type.

void discoverServices(String serviceType, int protocolType, NsdManager.DiscoveryListener listener)

Initiate service discovery to browse for instances of a service type.

void discoverServices(String serviceType, int protocolType, Network network, Executor executor, NsdManager.DiscoveryListener listener)

Initiate service discovery to browse for instances of a service type.

void registerService(NsdServiceInfo serviceInfo, int protocolType, NsdManager.RegistrationListener listener)

Register a service to be discovered by other services.

void registerService(AdvertisingRequest advertisingRequest, Executor executor, NsdManager.RegistrationListener listener)

Register a service to be discovered by other services.

void registerService(NsdServiceInfo serviceInfo, int protocolType, Executor executor, NsdManager.RegistrationListener listener)

Register a service to be discovered by other services.

void registerServiceInfoCallback(NsdServiceInfo serviceInfo, Executor executor, NsdManager.ServiceInfoCallback listener)

Register a callback to listen for updates to a service.

void registerServiceInfoCallback(DiscoveryRequest discoveryRequest, Executor executor, NsdManager.ServiceInfoCallback listener)

Register a callback to discover and track updates of services.

void resolveService(NsdServiceInfo serviceInfo, Executor executor, NsdManager.ResolveListener listener)

This method was deprecated in API level 34. the returned ServiceInfo may get stale at any time after resolution, including immediately after the callback is called, and may not contain some service information that could be delivered later, like additional host addresses. Prefer using registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback), which will keep the application up-to-date with the state of the service.

void resolveService(NsdServiceInfo serviceInfo, NsdManager.ResolveListener listener)

This method was deprecated in API level 34. the returned ServiceInfo may get stale at any time after resolution, including immediately after the callback is called, and may not contain some service information that could be delivered later, like additional host addresses. Prefer using registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback), which will keep the application up-to-date with the state of the service.

void stopServiceDiscovery(NsdManager.DiscoveryListener listener)

Stop service discovery initiated with discoverServices(DiscoveryRequest, Executor, DiscoveryListener).

void stopServiceResolution(NsdManager.ResolveListener listener)

Stop service resolution initiated with resolveService(NsdServiceInfo, ResolveListener).

void unregisterService(NsdManager.RegistrationListener listener)

Unregister a service registered through registerService(AdvertisingRequest, Executor, RegistrationListener).

void unregisterServiceInfoCallback(NsdManager.ServiceInfoCallback listener)

Unregister a callback registered with registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback).

Inherited methods

Constants

ACTION_NSD_STATE_CHANGED

Added in API level 16 
public static final String ACTION_NSD_STATE_CHANGED

Broadcast intent action to indicate whether network service discovery is enabled or disabled. An extra EXTRA_NSD_STATE provides the state information as int.

See also:

Constant Value: "android.net.nsd.STATE_CHANGED"

EXTRA_NSD_STATE

Added in API level 16 
public static final String EXTRA_NSD_STATE

The lookup key for an int that indicates whether network service discovery is enabled or disabled. Retrieve it with android.content.Intent.getIntExtra(String,int).

Constant Value: "nsd_state"

FAILURE_ALREADY_ACTIVE

Added in API level 16 
public static final int FAILURE_ALREADY_ACTIVE

Indicates that the operation failed because it is already active.

Constant Value: 3 (0x00000003)

FAILURE_BAD_PARAMETERS

Added in API level 34
Also in T Extensions 7 
public static final int FAILURE_BAD_PARAMETERS

Indicates that the service has failed to resolve because of bad parameters. This failure is passed with ServiceInfoCallback.onServiceInfoCallbackRegistrationFailed.

Constant Value: 6 (0x00000006)

FAILURE_INTERNAL_ERROR

Added in API level 16 
public static final int FAILURE_INTERNAL_ERROR

Failures are passed with RegistrationListener.onRegistrationFailed, RegistrationListener.onUnregistrationFailed, DiscoveryListener.onStartDiscoveryFailed, DiscoveryListener.onStopDiscoveryFailed or ResolveListener.onResolveFailed. Indicates that the operation failed due to an internal error.

Constant Value: 0 (0x00000000)

FAILURE_MAX_LIMIT

Added in API level 16 
public static final int FAILURE_MAX_LIMIT

Indicates that the operation failed because the maximum outstanding requests from the applications have reached.

Constant Value: 4 (0x00000004)

FAILURE_OPERATION_NOT_RUNNING

Added in API level 34
Also in T Extensions 7 
public static final int FAILURE_OPERATION_NOT_RUNNING

Indicates that the stop operation failed because it is not running. This failure is passed with ResolveListener.onStopResolutionFailed.

Constant Value: 5 (0x00000005)

FAILURE_PERMISSION_DENIED

Added in API level 37
Also in T Extensions 22 
public static final int FAILURE_PERMISSION_DENIED

Indicates that the operation failed because the caller did not have the required permissions. This can happen when trying to perform resolution, discovery, or callback registration without the Manifest.permission.ACCESS_LOCAL_NETWORK permission. This failure is passed with ResolveListener.onResolveFailed, DiscoveryListener.onStartDiscoveryFailed, or ServiceInfoCallback.onServiceInfoCallbackRegistrationFailed.

Constant Value: 7 (0x00000007)

NSD_STATE_DISABLED

Added in API level 16 
public static final int NSD_STATE_DISABLED

Network service discovery is disabled

Constant Value: 1 (0x00000001)

NSD_STATE_ENABLED

Added in API level 16 
public static final int NSD_STATE_ENABLED

Network service discovery is enabled

Constant Value: 2 (0x00000002)

PROTOCOL_DNS_SD

Added in API level 16 
public static final int PROTOCOL_DNS_SD

Dns based service discovery protocol

Constant Value: 1 (0x00000001)

SERVICE_PERMISSION_DENIED

Added in API level 37
Also in T Extensions 22 
public static final int SERVICE_PERMISSION_DENIED

Indicates the caller is not allowed to register service info callbacks or resolve a service.

This is a result code for checkPermissionForService(String,String,Executor,IntConsumer).

Constant Value: 2 (0x00000002)

SERVICE_PERMISSION_GRANTED

Added in API level 37
Also in T Extensions 22 
public static final int SERVICE_PERMISSION_GRANTED

Indicates the caller can register service info callbacks or resolve a service.

This is a result code for checkPermissionForService(String,String,Executor,IntConsumer).

Constant Value: 1 (0x00000001)

Public methods

checkPermissionForService

Added in API level 37
Also in T Extensions 22 
public void checkPermissionForService (String serviceName, 
                String serviceType, 
                Executor executor, 
                IntConsumer resultReceiver)

Check whether the caller can register service info callbacks or resolve a service.

Starting from target SDK Build.VERSION_CODES.CINNAMON_BUN, unless apps have the Manifest.permission.ACCESS_LOCAL_NETWORK permission, they can only register service info callbacks or resolve services that were selected in a UI picker, as per DiscoveryRequest.FLAG_SHOW_PICKER.

The system will remember whether a user has selected a service in the past, but access may be revoked for storage reasons or by the user. This method allows checking whether access to the service was granted in the picker and not revoked.

The resultReceiver will be called using the provided Executor with either SERVICE_PERMISSION_GRANTED or SERVICE_PERMISSION_DENIED.

Parameters
serviceName String: Instance name of the service.
This value cannot be null.
serviceType String: Type of the service, e.g. _ipp._tcp.
This value cannot be null.
executor Executor: The Executor on which to invoke the receiver.
This value cannot be null.
resultReceiver IntConsumer: The IntConsumer to receive the permission check result code; will be either SERVICE_PERMISSION_GRANTED or SERVICE_PERMISSION_DENIED.
This value cannot be null.

discoverServices

Added in API level 33
Also in T Extensions 3 
public void discoverServices (String serviceType, 
                int protocolType, 
                NetworkRequest networkRequest, 
                Executor executor, 
                NsdManager.DiscoveryListener listener)

Initiate service discovery to browse for instances of a service type. Service discovery consumes network bandwidth and will continue until the application calls stopServiceDiscovery(DiscoveryListener).

The function call immediately returns after sending a request to start service discovery to the framework. The application is notified of a success to initiate discovery through the callback DiscoveryListener.onDiscoveryStarted or a failure through DiscoveryListener.onStartDiscoveryFailed.

Upon successful start, application is notified when a service is found with DiscoveryListener.onServiceFound or when a service is lost with DiscoveryListener.onServiceLost.

Upon failure to start, service discovery is not active and application does not need to invoke stopServiceDiscovery(DiscoveryListener)

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

During discovery, new networks may connect or existing networks may disconnect - for example if wifi is reconnected. When a service was found on a network that disconnects, DiscoveryListener.onServiceLost will be called. If a new network connects that matches the NetworkRequest, DiscoveryListener.onServiceFound will be called for services found on that network. Applications that do not want to track networks themselves are encouraged to use this method instead of other overloads of discoverServices, as they will receive proper notifications when a service becomes available or unavailable due to network changes.
Requires Manifest.permission.ACCESS_NETWORK_STATE

Parameters
serviceType String: The service type being discovered. Examples include "_http._tcp" for http services or "_ipp._tcp" for printers.
This value cannot be null.
protocolType int: The service discovery protocol
networkRequest NetworkRequest: Request specifying networks that should be considered when discovering.
This value cannot be null.
executor Executor: Executor to run listener callbacks with.
This value cannot be null.
listener NsdManager.DiscoveryListener: The listener notifies of a successful discovery and is used to stop discovery on this serviceType through a call on stopServiceDiscovery(DiscoveryListener).
This value cannot be null.

discoverServices

Added in API level 35
Also in T Extensions 3 
public void discoverServices (DiscoveryRequest discoveryRequest, 
                Executor executor, 
                NsdManager.DiscoveryListener listener)

Initiates service discovery to browse for instances of a service type. Service discovery consumes network bandwidth and will continue until the application calls stopServiceDiscovery(DiscoveryListener).

The function call immediately returns after sending a request to start service discovery to the framework. The application is notified of a success to initiate discovery through the callback DiscoveryListener.onDiscoveryStarted or a failure through DiscoveryListener.onStartDiscoveryFailed.

Upon successful start, application is notified when a service is found with DiscoveryListener.onServiceFound or when a service is lost with DiscoveryListener.onServiceLost.

Upon failure to start, service discovery is not active and application does not need to invoke stopServiceDiscovery(DiscoveryListener)

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

Parameters
discoveryRequest DiscoveryRequest: the DiscoveryRequest object which specifies the discovery parameters such as service type, subtype and network.
This value cannot be null.
executor Executor: Executor to run listener callbacks with.
This value cannot be null.
listener NsdManager.DiscoveryListener: The listener notifies of a successful discovery and is used to stop discovery on this serviceType through a call on stopServiceDiscovery(DiscoveryListener).
This value cannot be null.

discoverServices

Added in API level 16
Also in T Extensions 3 
public void discoverServices (String serviceType, 
                int protocolType, 
                NsdManager.DiscoveryListener listener)

Initiate service discovery to browse for instances of a service type. Service discovery consumes network bandwidth and will continue until the application calls stopServiceDiscovery(DiscoveryListener).

The function call immediately returns after sending a request to start service discovery to the framework. The application is notified of a success to initiate discovery through the callback DiscoveryListener.onDiscoveryStarted or a failure through DiscoveryListener.onStartDiscoveryFailed.

Upon successful start, application is notified when a service is found with DiscoveryListener.onServiceFound or when a service is lost with DiscoveryListener.onServiceLost.

Upon failure to start, service discovery is not active and application does not need to invoke stopServiceDiscovery(DiscoveryListener)

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

Parameters
serviceType String: The service type being discovered. Examples include "_http._tcp" for http services or "_ipp._tcp" for printers
protocolType int: The service discovery protocol
listener NsdManager.DiscoveryListener: The listener notifies of a successful discovery and is used to stop discovery on this serviceType through a call on stopServiceDiscovery(DiscoveryListener). Cannot be null. Cannot be in use for an active service discovery.

discoverServices

Added in API level 33
Also in T Extensions 3 
public void discoverServices (String serviceType, 
                int protocolType, 
                Network network, 
                Executor executor, 
                NsdManager.DiscoveryListener listener)

Initiate service discovery to browse for instances of a service type. Service discovery consumes network bandwidth and will continue until the application calls stopServiceDiscovery(DiscoveryListener).

The function call immediately returns after sending a request to start service discovery to the framework. The application is notified of a success to initiate discovery through the callback DiscoveryListener.onDiscoveryStarted or a failure through DiscoveryListener.onStartDiscoveryFailed.

Upon successful start, application is notified when a service is found with DiscoveryListener.onServiceFound or when a service is lost with DiscoveryListener.onServiceLost.

Upon failure to start, service discovery is not active and application does not need to invoke stopServiceDiscovery(DiscoveryListener)

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

Parameters
serviceType String: The service type being discovered. Examples include "_http._tcp" for http services or "_ipp._tcp" for printers.
This value cannot be null.
protocolType int: The service discovery protocol
network Network: Network to discover services on, or null to discover on all available networks
executor Executor: Executor to run listener callbacks with.
This value cannot be null.
listener NsdManager.DiscoveryListener: The listener notifies of a successful discovery and is used to stop discovery on this serviceType through a call on stopServiceDiscovery(DiscoveryListener).
This value cannot be null.

registerService

Added in API level 16
Also in T Extensions 3 
public void registerService (NsdServiceInfo serviceInfo, 
                int protocolType, 
                NsdManager.RegistrationListener listener)

Register a service to be discovered by other services.

The function call immediately returns after sending a request to register service to the framework. The application is notified of a successful registration through the callback RegistrationListener.onServiceRegistered or a failure through RegistrationListener.onRegistrationFailed.

The application should call unregisterService(RegistrationListener) when the service registration is no longer required, and/or whenever the application is stopped.

Parameters
serviceInfo NsdServiceInfo: The service being registered
protocolType int: The service discovery protocol
listener NsdManager.RegistrationListener: The listener notifies of a successful registration and is used to unregister this service through a call on unregisterService(RegistrationListener). Cannot be null. Cannot be in use for an active service registration.

registerService

Added in version 36.1
Also in T Extensions 3 
public void registerService (AdvertisingRequest advertisingRequest, 
                Executor executor, 
                NsdManager.RegistrationListener listener)

Register a service to be discovered by other services.

The function call immediately returns after sending a request to register service to the framework. The application is notified of a successful registration through the callback RegistrationListener.onServiceRegistered or a failure through RegistrationListener.onRegistrationFailed.

The application should call unregisterService(RegistrationListener) when the service registration is no longer required, and/or whenever the application is stopped.

Parameters
advertisingRequest AdvertisingRequest: service being registered.
This value cannot be null.
executor Executor: Executor to run listener callbacks with.
This value cannot be null.
listener NsdManager.RegistrationListener: The listener notifies of a successful registration and is used to unregister this service through a call on unregisterService(RegistrationListener). Cannot be null.

registerService

Added in API level 33
Also in T Extensions 3 
public void registerService (NsdServiceInfo serviceInfo, 
                int protocolType, 
                Executor executor, 
                NsdManager.RegistrationListener listener)

Register a service to be discovered by other services.

The function call immediately returns after sending a request to register service to the framework. The application is notified of a successful registration through the callback RegistrationListener.onServiceRegistered or a failure through RegistrationListener.onRegistrationFailed.

The application should call unregisterService(RegistrationListener) when the service registration is no longer required, and/or whenever the application is stopped.

Parameters
serviceInfo NsdServiceInfo: The service being registered.
This value cannot be null.
protocolType int: The service discovery protocol
executor Executor: Executor to run listener callbacks with.
This value cannot be null.
listener NsdManager.RegistrationListener: The listener notifies of a successful registration and is used to unregister this service through a call on unregisterService(RegistrationListener). Cannot be null.

registerServiceInfoCallback

Added in API level 34
Also in T Extensions 7 
public void registerServiceInfoCallback (NsdServiceInfo serviceInfo, 
                Executor executor, 
                NsdManager.ServiceInfoCallback listener)

Register a callback to listen for updates to a service. An application can listen to a service to continuously monitor availability of given service. The callback methods will be called on the passed executor. And service updates are sent with continuous calls to ServiceInfoCallback.onServiceUpdated. This is different from resolveService(NsdServiceInfo, ResolveListener) which provides one shot service information.

This API listens to updates for one service at a time. Applications need to cancel the registration before registering the same callback instance again. Upon failure to register a callback for example if it's a duplicated registration, the application is notified through ServiceInfoCallback.onServiceInfoCallbackRegistrationFailed with FAILURE_BAD_PARAMETERS.

Parameters
serviceInfo NsdServiceInfo: the service to receive updates for.
This value cannot be null.
executor Executor: Executor to run callbacks with.
This value cannot be null.
listener NsdManager.ServiceInfoCallback: to receive callback upon service update.
This value cannot be null.

registerServiceInfoCallback

Added in API level 37
Also in T Extensions 7 
public void registerServiceInfoCallback (DiscoveryRequest discoveryRequest, 
                Executor executor, 
                NsdManager.ServiceInfoCallback listener)

Register a callback to discover and track updates of services.

This method combines discoverServices(DiscoveryRequest,Executor,DiscoveryListener) and registerServiceInfoCallback(NsdServiceInfo,Executor,ServiceInfoCallback) by finding services as per the provided DiscoveryRequest, and continuously monitoring availability and properties of the discovered services.

This API may cause more network traffic than using discoverServices(DiscoveryRequest,Executor,DiscoveryListener) and only calling registerServiceInfoCallback(NsdServiceInfo,Executor,ServiceInfoCallback) for select services, because it automatically queries all service information for all discovered services. However most mDNS advertisers reply with their full service information in one discovery reply, in which case there is no additional traffic, and this API saves the cost of registering multiple listeners for discovering and resolving services.

Applications need to cancel the registration before registering the same callback instance again. Upon failure to register a callback, the application is notified through ServiceInfoCallback.onServiceInfoCallbackRegistrationFailed.

Parameters
discoveryRequest DiscoveryRequest: the DiscoveryRequest object which specifies the discovery parameters such as service type, subtype and network.
This value cannot be null.
executor Executor: Executor to run listener callbacks with.
This value cannot be null.
listener NsdManager.ServiceInfoCallback: The listener to be notified of found, updated or lost services.
This value cannot be null.

resolveService

Added in API level 33
Also in T Extensions 3
Deprecated in API level 34 
public void resolveService (NsdServiceInfo serviceInfo, 
                Executor executor, 
                NsdManager.ResolveListener listener)

This method was deprecated in API level 34.
the returned ServiceInfo may get stale at any time after resolution, including immediately after the callback is called, and may not contain some service information that could be delivered later, like additional host addresses. Prefer using registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback), which will keep the application up-to-date with the state of the service.

Resolve a discovered service. An application can resolve a service right before establishing a connection to fetch the IP and port details on which to setup the connection.

Parameters
serviceInfo NsdServiceInfo: service to be resolved.
This value cannot be null.
executor Executor: Executor to run listener callbacks with.
This value cannot be null.
listener NsdManager.ResolveListener: to receive callback upon success or failure.
This value cannot be null.

resolveService

Added in API level 16
Also in T Extensions 3
Deprecated in API level 34 
public void resolveService (NsdServiceInfo serviceInfo, 
                NsdManager.ResolveListener listener)

This method was deprecated in API level 34.
the returned ServiceInfo may get stale at any time after resolution, including immediately after the callback is called, and may not contain some service information that could be delivered later, like additional host addresses. Prefer using registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback), which will keep the application up-to-date with the state of the service.

Resolve a discovered service. An application can resolve a service right before establishing a connection to fetch the IP and port details on which to setup the connection.

Parameters
serviceInfo NsdServiceInfo: service to be resolved
listener NsdManager.ResolveListener: to receive callback upon success or failure. Cannot be null. Cannot be in use for an active service resolution.

stopServiceDiscovery

Added in API level 16 
public void stopServiceDiscovery (NsdManager.DiscoveryListener listener)

Stop service discovery initiated with discoverServices(DiscoveryRequest, Executor, DiscoveryListener). An active service discovery is notified to the application with DiscoveryListener.onDiscoveryStarted and it stays active until the application invokes a stop service discovery. A successful stop is notified to with a call to DiscoveryListener.onDiscoveryStopped.

Upon failure to stop service discovery, application is notified through DiscoveryListener.onStopDiscoveryFailed.

If the listener is not already registered, for apps running on devices with T SDK extension < 22, this will throw with IllegalArgumentException.

Parameters
listener NsdManager.DiscoveryListener: This should be the listener object that was passed to discoverServices(DiscoveryRequest, Executor, DiscoveryListener). It identifies the discovery that should be stopped and notifies of a successful or unsuccessful stop. In API versions 20 and above, the listener object may be used for another service discovery once the callback has been called. In API versions <= 19, there is no entirely reliable way to know when a listener may be re-used, and a new listener should be created for each service discovery request.

stopServiceResolution

Added in API level 34
Also in T Extensions 7 
public void stopServiceResolution (NsdManager.ResolveListener listener)

Stop service resolution initiated with resolveService(NsdServiceInfo, ResolveListener). A successful stop is notified with a call to ResolveListener.onResolutionStopped.

Upon failure to stop service resolution for example if resolution is done or the requester stops resolution repeatedly, the application is notified ResolveListener.onStopResolutionFailed with FAILURE_OPERATION_NOT_RUNNING

If the listener is not already registered, for apps running on devices with T SDK extension < 22, this will throw with IllegalArgumentException.

Parameters
listener NsdManager.ResolveListener: This should be a listener object that was passed to resolveService(NsdServiceInfo, ResolveListener). It identifies the resolution that should be stopped and notifies of a successful or unsuccessful stop.
This value cannot be null.

unregisterService

Added in API level 16 
public void unregisterService (NsdManager.RegistrationListener listener)

Unregister a service registered through registerService(AdvertisingRequest, Executor, RegistrationListener). A successful unregister is notified to the application with a call to RegistrationListener.onServiceUnregistered.

Parameters
listener NsdManager.RegistrationListener: This should be the listener object that was passed to registerService(AdvertisingRequest, Executor, RegistrationListener). It identifies the service that should be unregistered and notifies of a successful or unsuccessful unregistration via the listener callbacks. In API versions 20 and above, the listener object may be used for another service registration once the callback has been called. In API versions <= 19, there is no entirely reliable way to know when a listener may be re-used, and a new listener should be created for each service registration request.

If the listener is not already registered, for apps running on devices with T SDK extension < 22, this will throw with IllegalArgumentException.

unregisterServiceInfoCallback

Added in API level 34
Also in T Extensions 7 
public void unregisterServiceInfoCallback (NsdManager.ServiceInfoCallback listener)

Unregister a callback registered with registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback). A successful unregistration is notified with a call to ServiceInfoCallback.onServiceInfoCallbackUnregistered. The same callback can only be reused after this is called.

If the listener is not already registered, for apps running on devices with T SDK extension < 22, this will throw with IllegalArgumentException.

Parameters
listener NsdManager.ServiceInfoCallback: This should be a listener object that was passed to registerServiceInfoCallback(DiscoveryRequest, Executor, ServiceInfoCallback). It identifies the registration that should be unregistered and notifies of a successful or unsuccessful stop.
This value cannot be null.