Managed SIP application as forking proxy
Learn how a forking proxy in a managed SIP application forwards a SIP request to multiple SIP address and returns the responses to the sender. This topic discusses the object model for the forking behavior.
Applies to: Lync Server 2013
SIP forking proxy application
In Microsoft Lync Server 2013 SDK, you can use the Microsoft SIP Processing Language (MSPL) message filter to fork basic proxies.
SIP forking proxy behavior
The following illustration shows the basic flow of a forking proxy.
.jpg "SIP Forking Proxy Transaction")
When a message is dispatched to the application by the MSPL script, a RequestReceivedEventArgs object is returned to the method inside the application that is designated by the Dispatch call. Attached to this object is a new ServerTransaction object, which contains the Request object as the ServerTransaction.Request property.
To fork the Request, clone ServerTransaction.Request for each recipient. First, ensure that the ServerTransaction.EnableForking property is set to true. If this property is set to false (the default is true), ArgumentException is thrown when you call ServerTransaction.CreateBranch again.
For each proxied request, call ServerTransaction.CreateBranch and then immediately call ClientTransaction.SendRequest, passing in the cloned Request.
Responses are handled asynchronously through the ResponseReceivedEventHandler delegate. The ClientTransaction.ResponseReceived event is triggered when a response for a sent Request is received, and the corresponding Response object is returned as the ResponseReceivedEventArgs.Response property.
To proxy the response, call ServerTransaction.SendResponse, passing in ResponseReceivedEventArgs.Response.
When a final response is passed to the server transaction, the object space that contains the ServerTransaction and its branches is automatically disposed of by the server agent, unless the ServerTransaction.Close() method on ServerTransaction was overridden.