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 seperate 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 informationAn 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, NsdManager.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
onServiceRegistered(NsdServiceInfo)
and a failure to register is notified
over onRegistrationFailed(NsdServiceInfo, int)
A peer application looking for http services can initiate a discovery for "_http._tcp"
with a call to discoverServices(String, int, NsdManager.DiscoveryListener)
. A service found is notified with a callback
to onServiceFound(NsdServiceInfo)
and a service lost is notified on
onServiceLost(NsdServiceInfo)
.
Once the peer application discovers the "Example" http srevice, and needs to receive data
from the "Example" application, it can initiate a resolve with resolveService(NsdServiceInfo, NsdManager.ResolveListener)
to
resolve the host and port details for the purpose of establishing a connection. A successful
resolve is notified on onServiceResolved(NsdServiceInfo)
and a failure is notified
on onResolveFailed(NsdServiceInfo, int)
.
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
Get an instance of this class by calling Context.getSystemService(Context.NSD_SERVICE)
.
Nested Classes | |||||||||||
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NsdManager.DiscoveryListener | Interface for callback invocation for service discovery | ||||||||||
NsdManager.RegistrationListener | Interface for callback invocation for service registration | ||||||||||
NsdManager.ResolveListener | Interface for callback invocation for service resolution |
Constants | |||||||||||
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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_INTERNAL_ERROR | Failures are passed with onRegistrationFailed(NsdServiceInfo, int) ,
onUnregistrationFailed(NsdServiceInfo, int) ,
onStartDiscoveryFailed(String, int) ,
onStopDiscoveryFailed(String, int) or onResolveFailed(NsdServiceInfo, int) . |
|||||||||
int | FAILURE_MAX_LIMIT | Indicates that the operation failed because the maximum outstanding requests from the applications have reached. | |||||||||
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 | |||||||||||
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Initiate service discovery to browse for instances of a service type.
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Register a service to be discovered by other services.
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Resolve a discovered service.
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Stop service discovery initiated with
discoverServices(String, int, NsdManager.DiscoveryListener) . | |||||||||||
Unregister a service registered through
registerService(NsdServiceInfo, int, NsdManager.RegistrationListener) . |
[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
|
Broadcast intent action to indicate whether network service discovery is
enabled or disabled. An extra EXTRA_NSD_STATE
provides the state
information as int.
The lookup key for an int that indicates whether network service discovery is enabled
or disabled. Retrieve it with getIntExtra(String, int)
.
Indicates that the operation failed because it is already active.
Failures are passed with onRegistrationFailed(NsdServiceInfo, int)
,
onUnregistrationFailed(NsdServiceInfo, int)
,
onStartDiscoveryFailed(String, int)
,
onStopDiscoveryFailed(String, int)
or onResolveFailed(NsdServiceInfo, int)
.
Indicates that the operation failed due to an internal error.
Indicates that the operation failed because the maximum outstanding requests from the applications have reached.
Network service discovery is disabled
Network service discovery is enabled
Dns based service discovery protocol
Initiate service discovery to browse for instances of a service type. Service discovery
consumes network bandwidth and will continue until the application calls
stopServiceDiscovery(NsdManager.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 onDiscoveryStarted(String)
or a failure
through onStartDiscoveryFailed(String, int)
.
Upon successful start, application is notified when a service is found with
onServiceFound(NsdServiceInfo)
or when a service is lost with
onServiceLost(NsdServiceInfo)
.
Upon failure to start, service discovery is not active and application does
not need to invoke stopServiceDiscovery(NsdManager.DiscoveryListener)
The application should call stopServiceDiscovery(NsdManager.DiscoveryListener)
when discovery of this
service type is no longer required, and/or whenever the application is paused or
stopped.
serviceType | The service type being discovered. Examples include "_http._tcp" for http services or "_ipp._tcp" for printers |
---|---|
protocolType | The service discovery protocol |
listener | The listener notifies of a successful discovery and is used
to stop discovery on this serviceType through a call on stopServiceDiscovery(NsdManager.DiscoveryListener) .
Cannot be null. Cannot be in use for an active service discovery.
|
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 onServiceRegistered(NsdServiceInfo)
or a failure
through onRegistrationFailed(NsdServiceInfo, int)
.
The application should call unregisterService(NsdManager.RegistrationListener)
when the service
registration is no longer required, and/or whenever the application is stopped.
serviceInfo | The service being registered |
---|---|
protocolType | The service discovery protocol |
listener | The listener notifies of a successful registration and is used to
unregister this service through a call on unregisterService(NsdManager.RegistrationListener) . Cannot be null.
Cannot be in use for an active service registration.
|
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.
serviceInfo | service to be resolved |
---|---|
listener | to receive callback upon success or failure. Cannot be null. Cannot be in use for an active service resolution. |
Stop service discovery initiated with discoverServices(String, int, NsdManager.DiscoveryListener)
. An active service
discovery is notified to the application with onDiscoveryStarted(String)
and it stays active until the application invokes a stop service discovery. A successful
stop is notified to with a call to onDiscoveryStopped(String)
.
Upon failure to stop service discovery, application is notified through
onStopDiscoveryFailed(String, int)
.
listener | This should be the listener object that was passed to discoverServices(String, int, NsdManager.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.
|
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Unregister a service registered through registerService(NsdServiceInfo, int, NsdManager.RegistrationListener)
. A successful
unregister is notified to the application with a call to
onServiceUnregistered(NsdServiceInfo)
.
listener | This should be the listener object that was passed to
registerService(NsdServiceInfo, int, NsdManager.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.
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