How to use dum
The DialogUsageManager(or DUM) is the unit that keeps track of all of the Dialog related data structures and sits on top of the transaction layer of the SIP stack. It keeps track of multiple DialogSets which contain Dialogs. Each DialogSet contains all the Dialogs that were created by a common initial request. They all share the same SIP Call-Id and from tag from the orginal request. Inside a specific DialogSet there can be some type of BaseCreator that represents the intial request that generated the dialog. This will only exist on the UAC side. The DialogSet also contains several objects derived from BaseUsage that are using this particular dialog. There are several types of things that are a Usage of a dialog. There can be one InviteSession, one Registration, one Publication, multiple Subscriptions and multiple OutOfDialogRequests. Note the name OutOfDialog is a little weird - OutOfDialog requests are actually in a thing a lot like a dialog but are transactions that are not in one of the other categories. Typically messages that result in OutOfDialogRequests are MESSAGE and OPTIONS.
An initial SIP Request is created by calling the makeX interfaces on the DUM. It is then sent using the send interface on the DUM. When a response is returned for the request, a callback from one of the Handler classes will be called to notify the application about the incoming events. This will pass up some type of client or server usages class that can be used to send aditional messages and responses in the context of this particularr usage of the Dialog.
- Main class that keeps track of all the DialogSet, Dialog, and Usage objects.
- User Agent Server (UAS)
- A user agent server is a logical entity that generates a response to a SIP request. The response accepts, rejects, or redirects the request. This role lasts only for the duration of that transaction. In other words, if a piece of software responds to a request, it acts as a UAS for the duration of that transaction. If it generates a request later, it assumes the role of a user agent client for the processing of that transaction. (Definition from http://www.faqs.org/rfcs/rfc3261.html)
- User Agent Client (UAC)
- A user agent client is a logical entity that creates a new request, and then uses the client transaction state machinery to send it. The role of UAC lasts only for the duration of that transaction. In other words, if a piece of software initiates a request, it acts as a UAC for the duration of that transaction. If it receives a request later, it assumes the role of a user agent server for the processing of that transaction. (Definition from http://www.faqs.org/rfcs/rfc3261.html)
- A container class that will hold a set of dialogs that were generated from a common request. They share the same call-id and the same from tag in the request that generated the dialog.
- A term to generically describe the container for the usage created from a non-dialog creating request such as REGISTER or PUBLISH. Monologs exist for both the UAC and UAS.
- A container holding such things and local and remote CSEQ, URI, Call-ID and such as defined by the SIP standard.
- An identifier that uniquely finds a a Dialog by Call-ID, and To and From tags.
- An identifier that uniquily identifies a Dialog-Set and is formed from Call-ID and From tag.
- These are the objects are are using a dialog. They include ClientInviteSession, ClientOutOfDialogReq, ClientPublication, ClientRegistration, ClientSubscription, ServerInviteSession, ServerOutOfDialogReq, ServerPublication, ServerRegistration, and ServerSubscription.
- These are objects uses to derive class from that allow callbacks from this layer to the application. They include InviteSessionHandler, OutOfDialogHandler, RegistrationHandler, SubscriptionHandler, and PublictionHandler.
- All the Usages and Handlers are not really exposed to the applications using this layer. Instead, handles to them are passed out. When the applications goes to use a handle, the underlying object may have been deleted and the applications must be prepared for this not to work.