Activity sharing: Difference between revisions
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[[Image:Dbus communication.png|thumb|500px]] |
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{{Translations}} |
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== Overview == |
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Collaboration in Sugar activities works using a set of services that run on the laptop, and APIs in the Sugar Python modules that wrap those services. The main services are the '''Telepathy connection managers''' and the '''[[Presence Service]]''' that coordinates them. |
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Telepathy is a system describing a generic interface for multi-user chat (MUC), instant messaging (IM) and voice/video applications. It is the underlying infrastructure used by Sugar. |
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[[Image:shared activites.png|center]] |
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The generic telepathy interface specification can be found at http://telepathy.freedesktop.org/ |
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[http://telepathy.freedesktop.org/ Telepathy] is a system describing a generic interface for various kinds of communication. It is the underlying infrastructure used by Sugar for collaboration. Currently, two Telepathy implementations are used: [[Telepathy Gabble|Gabble]], for Jabber, and [[Telepathy Salut|Salut]] for serverless Jabber (a.k.a. link-local XMPP). The former is used when the school server is reachable; the latter in the simple mesh case. |
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==PresenceService== |
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The presence service is a part of Sugar that tracks other Buddies and Activities on the network. It is designed to have a D-Bus interface that is to be used by applications. To make life easier, though, there is a class that takes care of talking to the D-Bus presence service (sugar.presence.PresenceService). In fact, you'll probably only have to use that. |
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== Advertisements and invitations == |
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Currently the presence service uses Gabble, a telepathy 'Connection Manager' that provides server-based Jabber/XMPP functionality. It talks to a server (olpc.collabora.co.uk) and sets up different chat rooms through which activities talk to each other. Salut, a link-local Connection Manager using reliable multicast over the local network, is currently being integrated; the presence service will use Salut at all times, and Gabble when it can see the server, preferring to use Gabble when available. |
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Shared sugar activities are discovered in two different ways: through broadcast advertisements, and through invitations. |
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Tubes offer a mechanism to provide a Dbus service that is shared between several different nodes in a network. They are part of libtelepathy as well. There is currently only one implementation within telepathy that supports Tubes: Gabble (used by the presenceservice), so all tube connections currently require a chat-room on a server. Once a tube is available, it functions as a Dbus bus (like the session and system busses) that is shared between the different nodes. |
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Advertisements are made when the user tells the activity to share itself with the entire network. Anybody on the network can see the activity. |
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To use a tube the following actions are necessary: |
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#Create a Connection Manager object (Gabble) |
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#Get a Tubes channel |
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#Create or join a Tube |
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Invitations are send to particular users. Only those users who are sent an invitation see the activity (unless the activity has also been advertised). When Sugar recevies an invitation, it asks the user whether they want to accept or reject it. |
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===Sharing an object through the tube=== |
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The class you want to share should inherit from dbus.service.Object. Once you have the tube: |
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dbus.service.Object.__init__(self, self._tube, self._object_path) |
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===Calling a function on a remote object=== |
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Once you know the tube and the unique busname: |
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self._tube.get_object(busname, self._object_path).MyFunction(123) |
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[[Tubes]] are a means for shared activities to exchange data. There are currently two types of tubes: |
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===Subscribing to a signal=== |
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self._tube.add_signal_receiver(self._receive_my_sig, 'MySignal', \ |
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IFACE, path=self._object_path, sender_keyword='sender') |
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* '''D-Bus Tubes''' provide a D-Bus bus service that is shared between the participants in a shared activity, providing signals to all participants, and methods called on a particular participant. |
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* '''Stream Tubes''' provide a socket-like connection set up via XMPP, for data streaming like HTTP, between two participants. |
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The [[Presence Service]] creates connection manager objects (Gabble and/or |
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Gabble). PS creates or gets a Tubes channel. For Python Activities, Sugar |
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creates or joins a D-Bus tube automatically. |
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| ⚫ | The initiator of the activity should then call Tubes.OfferDBusTube to offer a Tube with a specific service name. When a buddy joins an activity, he will try to figure out which Tubes are available by calling Tubes.ListTubes() on the tubes channel (which he doesn't have to create anymore). Both OfferDBusTube and ListTubes result in a callback when the Tube becomes really available. Only then a working Tube is handed to the (shared) activity and it is possible to export objects on that bus and subscribe to signals etc. |
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See [[Collaboration Tutorial]] for more on using Tubes. |
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Buddies/nodes within an activity are currently identified with different handles by different components. The following handles can be distinguished: |
Buddies/nodes within an activity are currently identified with different handles by different components. The following handles can be distinguished: |
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*Dbus name. If you have a Dbus related function with the “sender” argument specified, this is what you'll get. To buddy object: |
*Dbus name. If you have a Dbus related function with the “sender” argument specified, this is what you'll get. To buddy object: |
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sugar.presence.PresenceService.get_buddy(buddy's |
sugar.presence.PresenceService.get_buddy(buddy's public key) |
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*Telepathy handle. To buddy object: |
*Telepathy handle. To buddy object: |
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sugar.presence.PresenceService.get_buddy_by_telepathy_handle(tp_conn, tp_conn_path, handle) |
sugar.presence.PresenceService.get_buddy_by_telepathy_handle(tp_conn, tp_conn_path, handle) |
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== Interactions == |
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How the various components interact. |
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=== Presence Service ⟷ connection manager === |
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* org.freedesktop.Telepathy.ConnectionManager |
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** RequestConnection |
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* org.freedesktop.Telepathy.Connection |
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** RequestChannel |
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* org.laptop.Telepathy.BuddyInfo |
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* org.laptop.Telepathy.ActivityProperties |
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=== activity ⟷ Presence Service === |
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* org.laptop.Sugar.Presence |
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* org.laptop.Sugar.Presence.Buddy |
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* org.laptop.Sugar.Presence.Activity |
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=== activity ⟷ connection manager === |
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* org.freedesktop.Telepathy.Channel.Type.Tube |
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** OfferDBusTube |
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** OfferStreamTube |
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[[Category:Sugar]] |
[[Category:Sugar]] |
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[[Category:Developers]] |
[[Category:Developers]] |
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[[category:Collaboration]] |
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Latest revision as of 00:11, 9 July 2011
Overview
Collaboration in Sugar activities works using a set of services that run on the laptop, and APIs in the Sugar Python modules that wrap those services. The main services are the Telepathy connection managers and the Presence Service that coordinates them.
Telepathy is a system describing a generic interface for various kinds of communication. It is the underlying infrastructure used by Sugar for collaboration. Currently, two Telepathy implementations are used: Gabble, for Jabber, and Salut for serverless Jabber (a.k.a. link-local XMPP). The former is used when the school server is reachable; the latter in the simple mesh case.
Advertisements and invitations
Shared sugar activities are discovered in two different ways: through broadcast advertisements, and through invitations.
Advertisements are made when the user tells the activity to share itself with the entire network. Anybody on the network can see the activity.
Invitations are send to particular users. Only those users who are sent an invitation see the activity (unless the activity has also been advertised). When Sugar recevies an invitation, it asks the user whether they want to accept or reject it.
Tubes
Tubes are a means for shared activities to exchange data. There are currently two types of tubes:
- D-Bus Tubes provide a D-Bus bus service that is shared between the participants in a shared activity, providing signals to all participants, and methods called on a particular participant.
- Stream Tubes provide a socket-like connection set up via XMPP, for data streaming like HTTP, between two participants.
Using tubes in Sugar activities
The Presence Service creates connection manager objects (Gabble and/or Salut). It gets a Connection object (to the Jabber server in the case of Gabble). PS creates or gets a Tubes channel. For Python Activities, Sugar creates or joins a D-Bus tube automatically.
The initiator of the activity should then call Tubes.OfferDBusTube to offer a Tube with a specific service name. When a buddy joins an activity, he will try to figure out which Tubes are available by calling Tubes.ListTubes() on the tubes channel (which he doesn't have to create anymore). Both OfferDBusTube and ListTubes result in a callback when the Tube becomes really available. Only then a working Tube is handed to the (shared) activity and it is possible to export objects on that bus and subscribe to signals etc.
See Collaboration Tutorial for more on using Tubes.
Who's who?
Buddies/nodes within an activity are currently identified with different handles by different components. The following handles can be distinguished:
- Dbus name. If you have a Dbus related function with the “sender” argument specified, this is what you'll get. To buddy object:
sugar.presence.PresenceService.get_buddy(buddy's public key)
- Telepathy handle. To buddy object:
sugar.presence.PresenceService.get_buddy_by_telepathy_handle(tp_conn, tp_conn_path, handle)
Interactions
How the various components interact.
Presence Service ⟷ connection manager
- org.freedesktop.Telepathy.ConnectionManager
- RequestConnection
- org.freedesktop.Telepathy.Connection
- RequestChannel
- org.laptop.Telepathy.BuddyInfo
- org.laptop.Telepathy.ActivityProperties
activity ⟷ Presence Service
- org.laptop.Sugar.Presence
- org.laptop.Sugar.Presence.Buddy
- org.laptop.Sugar.Presence.Activity
activity ⟷ connection manager
- org.freedesktop.Telepathy.Channel.Type.Tube
- OfferDBusTube
- OfferStreamTube