org.deepsymmetry.beatlink

Class DeviceFinder

java.lang.Object

org.deepsymmetry.beatlink.LifecycleParticipant

org.deepsymmetry.beatlink.DeviceFinder

public class DeviceFinder
extends LifecycleParticipant

Watches for devices to report their presence by broadcasting announcement packets on port 50000, and keeps a list of the devices that have been seen, and the network address on which they were seen.

Author:

James Elliott

Field Summary

Fields

Modifier and Type	Field and Description
static int	ANNOUNCEMENT_PORT The port to which devices broadcast announcement messages to report their presence on the network.
static int	MAXIMUM_AGE The number of milliseconds after which we will consider a device to have disappeared if we have not received an announcement from it.

Method Summary

Modifier and Type	Method and Description
void	addDeviceAnnouncementListener(DeviceAnnouncementListener listener) Adds the specified device announcement listener to receive device announcements when DJ Link devices are found on or leave the network.
void	addIgnoredAddress(InetAddress address) Start ignoring any device updates which are received from the specified address.
Set<DeviceAnnouncement>	getCurrentDevices() Get the set of DJ Link devices which currently can be seen on the network.
Set<DeviceAnnouncementListener>	getDeviceAnnouncementListeners() Get the set of device announcement listeners that are currently registered.
long	getFirstDeviceTime() Get the timestamp of when we saw the first announcement packet, to help the VirtualCdj determine how long it needs to watch for devices in order to avoid conflicts when self-assigning a device number.
static DeviceFinder	getInstance() Get the singleton instance of this class.
DeviceAnnouncement	getLatestAnnouncementFrom(int deviceNumber) Find and return the device announcement that was most recently received from a device identifying itself with the specified device number, if any.
long	getStartTime() Get the timestamp of when we started listening for device announcements.
boolean	isRunning() Check whether we are presently listening for device announcements.
void	removeDeviceAnnouncementListener(DeviceAnnouncementListener listener) Removes the specified device announcement listener so that it no longer receives device announcements when DJ Link devices are found on or leave the network.
void	removeIgnoredAddress(InetAddress address) Stop ignoring device updates which are received from the specified address.
void	start() Start listening for device announcements and keeping track of the DJ Link devices visible on the network.
void	stop() Stop listening for device announcements.
String	toString()

Methods inherited from class org.deepsymmetry.beatlink.LifecycleParticipant

addLifecycleListener, deliverLifecycleAnnouncement, ensureRunning, getLifecycleListeners, removeLifecycleListener

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

ANNOUNCEMENT_PORT

public static final int ANNOUNCEMENT_PORT

The port to which devices broadcast announcement messages to report their presence on the network.

See Also:

Constant Field Values

MAXIMUM_AGE

public static final int MAXIMUM_AGE

The number of milliseconds after which we will consider a device to have disappeared if we have not received an announcement from it.

See Also:

Constant Field Values

Method Detail

isRunning

public boolean isRunning()

Check whether we are presently listening for device announcements.

Specified by:

isRunning in class LifecycleParticipant

Returns:

true if our socket is open and monitoring for DJ Link device announcements on the network

getStartTime

public long getStartTime()

Get the timestamp of when we started listening for device announcements.

Returns:

the system millisecond timestamp when start() was called.

Throws:

IllegalStateException - if we are not listening for announcements.

getFirstDeviceTime

public long getFirstDeviceTime()

Get the timestamp of when we saw the first announcement packet, to help the VirtualCdj determine how long it needs to watch for devices in order to avoid conflicts when self-assigning a device number.

Returns:

the system millisecond timestamp when the first device announcement was received.

Throws:

IllegalStateException - if we are not listening for announcements, or if none have been seen.

addIgnoredAddress

public void addIgnoredAddress(InetAddress address)

Start ignoring any device updates which are received from the specified address. Intended for use by the VirtualCdj, so that its updates do not cause it to appear as a device.

Parameters:

address - the address from which any device updates should be ignored.

removeIgnoredAddress

public void removeIgnoredAddress(InetAddress address)

Stop ignoring device updates which are received from the specified address. Intended for use by the VirtualCdj, so that when it shuts down, its socket stops being treated specially.

Parameters:

address - the address from which any device updates should be ignored.

start

public void start()
           throws SocketException

Start listening for device announcements and keeping track of the DJ Link devices visible on the network. If already listening, has no effect.

Throws:

SocketException - if the socket to listen on port 50000 cannot be created

stop

public void stop()

Stop listening for device announcements. Also discard any announcements which had been received, and notify any registered listeners that those devices have been lost.

getCurrentDevices

public Set<DeviceAnnouncement> getCurrentDevices()

Get the set of DJ Link devices which currently can be seen on the network. These can be passed to VirtualCdj.getLatestStatusFor(DeviceUpdate) to find the current detailed status for that device, as long as the Virtual CDJ is active.

Returns:

the devices which have been heard from recently enough to be considered present on the network

Throws:

IllegalStateException - if the DeviceFinder is not active

getLatestAnnouncementFrom

public DeviceAnnouncement getLatestAnnouncementFrom(int deviceNumber)

Find and return the device announcement that was most recently received from a device identifying itself with the specified device number, if any.

Parameters:

deviceNumber - the device number of interest

Returns:

the matching announcement or null if no such device has been heard from

Throws:

IllegalStateException - if the DeviceFinder is not active

addDeviceAnnouncementListener

public void addDeviceAnnouncementListener(DeviceAnnouncementListener listener)

Adds the specified device announcement listener to receive device announcements when DJ Link devices are found on or leave the network. If listener is null or already present in the list of registered listeners, no exception is thrown and no action is performed.

Device announcements are delivered to listeners on the Event Dispatch thread, so it is fine to interact with user interface objects in listener methods. Any code in the listener method must finish quickly, or unhandled events will back up and the user interface will be come unresponsive.

Parameters:

listener - the device announcement listener to add

removeDeviceAnnouncementListener

public void removeDeviceAnnouncementListener(DeviceAnnouncementListener listener)

Removes the specified device announcement listener so that it no longer receives device announcements when DJ Link devices are found on or leave the network. If listener is null or not present in the list of registered listeners, no exception is thrown and no action is performed.

Parameters:

listener - the device announcement listener to remove

getDeviceAnnouncementListeners

public Set<DeviceAnnouncementListener> getDeviceAnnouncementListeners()

Get the set of device announcement listeners that are currently registered.

Returns:

the currently registered device announcement listeners

getInstance

public static DeviceFinder getInstance()

Get the singleton instance of this class.

Returns:

the only instance of this class which exists.

toString

public String toString()

Overrides:

toString in class Object