NsdManager

public final class NsdManager
extends Object

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

The Network Service Discovery Manager class provides the API to discover services on a network. As an example, if device A and device B are connected over a Wi-Fi network, a game registered on device A can be discovered by a game on device B. Another example use case is an application discovering printers on the network.

The API currently supports DNS based service discovery and discovery is currently limited to a local network over Multicast DNS. DNS service discovery is described at http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt

The API is asynchronous, and responses to requests from an application are on listener callbacks on a separate internal thread.

There are three main operations the API supports - registration, discovery and resolution. 

                          Application start
                                 |
                                 |
                                 |                  onServiceRegistered()
                     Register any local services  /
                      to be advertised with       \
                       registerService()            onRegistrationFailed()
                                 |
                                 |
                          discoverServices()
                                 |
                      Maintain a list to track
                        discovered services
                                 |
                                 |--------->
                                 |          |
                                 |      onServiceFound()
                                 |          |
                                 |     add service to list
                                 |          |
                                 |<----------
                                 |
                                 |--------->
                                 |          |
                                 |      onServiceLost()
                                 |          |
                                 |   remove service from list
                                 |          |
                                 |<----------
                                 |
                                 |
                                 | Connect to a service
                                 | from list ?
                                 |
                          resolveService()
                                 |
                         onServiceResolved()
                                 |
                     Establish connection to service
                     with the host and port information
An application that needs to advertise itself over a network for other applications to discover it can do so with a call to registerService(NsdServiceInfo, int, RegistrationListener). If Example is a http based application that can provide HTML data to peer services, it can register a name "Example" with service type "_http._tcp". A successful registration is notified with a callback to RegistrationListener#onServiceRegistered and a failure to register is notified over RegistrationListener#onRegistrationFailed

A peer application looking for http services can initiate a discovery for "_http._tcp" with a call to discoverServices(DiscoveryRequest, Executor, DiscoveryListener). A service found is notified with a callback to DiscoveryListener#onServiceFound and a service lost is notified on DiscoveryListener#onServiceLost.

Once the peer application discovers the "Example" http service, and either needs to read the attributes of the service or wants to receive data from the "Example" application, it can initiate a resolve with resolveService(NsdServiceInfo, ResolveListener) to resolve the attributes, host, and port details. A successful resolve is notified on ResolveListener#onServiceResolved and a failure is notified on ResolveListener#onResolveFailed. Applications can reserve for a service type at http://www.iana.org/form/ports-service. Existing services can be found at http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml

See also:

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 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

Public methods

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

This method was deprecated in API level 36. 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(NsdServiceInfo, 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 36. 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(NsdServiceInfo, 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(NsdServiceInfo, int, RegistrationListener).

void unregisterServiceInfoCallback(NsdManager.ServiceInfoCallback listener)

Unregister a callback registered with registerServiceInfoCallback(NsdServiceInfo, 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 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)

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)

Public methods

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 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.

An application can listen to a service once a time. It needs to cancel the registration before registering other callbacks. 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.

resolveService

Added in API level 33
Also in T Extensions 3
Deprecated in API level 36 
public void resolveService (NsdServiceInfo serviceInfo, 
                Executor executor, 
                NsdManager.ResolveListener listener)

This method was deprecated in API level 36.
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(NsdServiceInfo, 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 36 
public void resolveService (NsdServiceInfo serviceInfo, 
                NsdManager.ResolveListener listener)

This method was deprecated in API level 36.
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(NsdServiceInfo, 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.

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

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. Throws IllegalArgumentException if the listener was not passed to resolveService before. This value cannot be null.

unregisterService

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

Unregister a service registered through registerService(NsdServiceInfo, int, 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(NsdServiceInfo, int, 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.

unregisterServiceInfoCallback

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

Unregister a callback registered with registerServiceInfoCallback(NsdServiceInfo, 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 callback is not already registered, this will throw with IllegalArgumentException.

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