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224 lines
8.8 KiB
Markdown
224 lines
8.8 KiB
Markdown
Service Discovery
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=================
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The service discovery extension allows to discover items and information about
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XMPP entities. Follow these links to learn how to use this extension.
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* Manage XMPP entity features
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* Provide node information
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* Discover items associated with an XMPP entity
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* Discover information about an XMPP entity
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* Publish publicly available items
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**XEP related:** [XEP-30](http://www.xmpp.org/extensions/xep-0030.html)
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Manage XMPP entity features
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---------------------------
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**Description**
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Any XMPP entity may receive a discovery request and must answer with its
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associated items or information. Therefore, your Smack client may receive a
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discovery request that must respond to (i.e., if your client supports XHTML-
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IM). This extension automatically responds to a discovery request with the
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information that you previously configured.
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**Usage**
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In order to configure the supported features by your client you should first
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obtain the ServiceDiscoveryManager associated with your XMPPConnection. To get
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your ServiceDiscoveryManager send **getInstanceFor(connection)** to the class
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_**ServiceDiscoveryManager**_ where connection is your XMPPConnection.
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Once you have your ServiceDiscoveryManager you will be able to manage the
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supported features. To register a new feature send **addFeature(feature)** to
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your _**ServiceDiscoveryManager**_ where feature is a String that represents
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the supported feature. To remove a supported feature send
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**removeFeature(feature)** to your _**ServiceDiscoveryManager**_ where feature
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is a String that represents the feature to remove.
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**Examples**
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In this example we can see how to add and remove supported features:
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```
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// Obtain the ServiceDiscoveryManager associated with my XMPP connection
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ServiceDiscoveryManager discoManager = ServiceDiscoveryManager.getInstanceFor(connection);
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// Register that a new feature is supported by this XMPP entity
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discoManager.addFeature(namespace1);
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// Remove the specified feature from the supported features
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discoManager.removeFeature(namespace2);
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```
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Provide node information
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------------------------
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**Description**
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Your XMPP entity may receive a discovery request for items non-addressable as
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a JID such as the MUC rooms where you are joined. In order to answer the
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correct information it is necessary to configure the information providers
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associated to the items/nodes within the Smack client.
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**Usage**
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In order to configure the associated nodes within the Smack client you will
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need to create a NodeInformationProvider and register it with the
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_**ServiceDiscoveryManager**_. To get your ServiceDiscoveryManager send
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**getInstanceFor(connection)** to the class _**ServiceDiscoveryManager**_
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where connection is your XMPPConnection.
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Once you have your ServiceDiscoveryManager you will be able to register
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information providers for the XMPP entity's nodes. To register a new node
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information provider send **setNodeInformationProvider(String node,
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NodeInformationProvider listener)** to your _**ServiceDiscoveryManager**_
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where node is the item non-addressable as a JID and listener is the
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_**NodeInformationProvider**_ to register. To unregister a
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_**NodeInformationProvider**_ send **removeNodeInformationProvider(String
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node)** to your _**ServiceDiscoveryManager**_ where node is the item non-
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addressable as a JID whose information provider we want to unregister.
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**Examples**
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In this example we can see how to register a NodeInformationProvider with a
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ServiceDiscoveryManager that will provide information concerning a node named
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"http://jabber.org/protocol/muc#rooms":
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```
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// Set the NodeInformationProvider that will provide information about the
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// joined rooms whenever a disco request is received
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ServiceDiscoveryManager.getInstanceFor(connection).setNodeInformationProvider(
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"http://jabber.org/protocol/muc#rooms",
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new NodeInformationProvider() {
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public List getNodeItems() {
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ArrayList answer = new ArrayList();
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Iterator rooms = MultiUserChat.getJoinedRooms(connection);
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while (rooms.hasNext()) {
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answer.add(new DiscoverItems.Item((String)rooms.next()));
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}
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return answer;
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}
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});
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```
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Discover items associated with an XMPP entity
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---------------------------------------------
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**Description**
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In order to obtain information about a specific item you have to first
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discover the items available in an XMPP entity.
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**Usage**
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Once you have your ServiceDiscoveryManager you will be able to discover items
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associated with an XMPP entity. To discover the items of a given XMPP entity
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send **discoverItems(entityID)** to your _**ServiceDiscoveryManager**_ where
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entityID is the ID of the entity. The message **discoverItems(entityID)** will
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answer an instance of _**DiscoverItems**_ that contains the discovered items.
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**Examples**
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In this example we can see how to discover the items associated with an online
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catalog service:
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```
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// Obtain the ServiceDiscoveryManager associated with my XMPPConnection
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ServiceDiscoveryManager discoManager = ServiceDiscoveryManager.getInstanceFor(connection);
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// Get the items of a given XMPP entity
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// This example gets the items associated with online catalog service
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DiscoverItems discoItems = discoManager.discoverItems("plays.shakespeare.lit");
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// Get the discovered items of the queried XMPP entity
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Iterator it = discoItems.getItems();
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// Display the items of the remote XMPP entity
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while (it.hasNext()) {
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DiscoverItems.Item item = (DiscoverItems.Item) it.next();
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System.out.println(item.getEntityID());
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System.out.println(item.getNode());
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System.out.println(item.getName());
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}
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```
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Discover information about an XMPP entity
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-----------------------------------------
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**Description**
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Once you have discovered the entity ID and name of an item, you may want to
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find out more about the item. The information desired generally is of two
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kinds: 1) The item's identity and 2) The features offered by the item.
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This information helps you determine what actions are possible with regard to
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this item (registration, search, join, etc.) as well as specific feature types
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of interest, if any (e.g., for the purpose of feature negotiation).
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**Usage**
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Once you have your ServiceDiscoveryManager you will be able to discover
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information associated with an XMPP entity. To discover the information of a
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given XMPP entity send **discoverInfo(entityID)** to your
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_**ServiceDiscoveryManager**_ where entityID is the ID of the entity. The
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message **discoverInfo(entityID)** will answer an instance of
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_**DiscoverInfo**_ that contains the discovered information.
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**Examples**
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In this example we can see how to discover the information of a conference
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room:
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```
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// Obtain the ServiceDiscoveryManager associated with my XMPPConnection
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ServiceDiscoveryManager discoManager = ServiceDiscoveryManager.getInstanceFor(connection);
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// Get the information of a given XMPP entity
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// This example gets the information of a conference room
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DiscoverInfo discoInfo = discoManager.discoverInfo("balconyscene@plays.shakespeare.lit");
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// Get the discovered identities of the remote XMPP entity
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Iterator it = discoInfo.getIdentities();
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// Display the identities of the remote XMPP entity
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while (it.hasNext()) {
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DiscoverInfo.Identity identity = (DiscoverInfo.Identity) it.next();
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System.out.println(identity.getName());
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System.out.println(identity.getType());
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System.out.println(identity.getCategory());
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}
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// Check if room is password protected
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discoInfo.containsFeature("muc_passwordprotected");
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```
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Publish publicly available items
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--------------------------------
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**Description**
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Publish your entity items to some kind of persistent storage. This enables
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other entities to query that entity using the disco#items namespace and
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receive a result even when the entity being queried is not online (or
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available).
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**Usage**
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Once you have your ServiceDiscoveryManager you will be able to publish items
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to some kind of persistent storage. To publish the items of a given XMPP
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entity you have to first create an instance of _**DiscoverItems**_ and
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configure it with the items to publish. Then you will have to send
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**publishItems(String entityID, DiscoverItems discoverItems)** to your
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_**ServiceDiscoveryManager**_ where entityID is the address of the XMPP entity
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that will persist the items and discoverItems contains the items to publish.
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**Examples**
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In this example we can see how to publish new items:
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```
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// Obtain the ServiceDiscoveryManager associated with my XMPPConnection
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ServiceDiscoveryManager discoManager = ServiceDiscoveryManager.getInstanceFor(connection);
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// Create a DiscoverItems with the items to publish
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DiscoverItems itemsToPublish = new DiscoverItems();
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DiscoverItems.Item itemToPublish = new DiscoverItems.Item("pubsub.shakespeare.lit");
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itemToPublish.setName("Avatar");
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itemToPublish.setNode("romeo/avatar");
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itemToPublish.setAction(DiscoverItems.Item.UPDATE_ACTION);
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itemsToPublish.addItem(itemToPublish);
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// Publish the new items by sending them to the server
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discoManager.publishItems("host", itemsToPublish);
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```
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