Managed SIP application as forwarding proxy

Learn how a forwarding proxy in a managed SIP application forwards a SIP request to a single SIP address and returns the responses to the sender. This topic discusses the object model for the forwarding behavior.

Applies to: Lync Server 2013

SIP forwarding proxy application

In Microsoft Lync Server 2013 SDK, you can use the Microsoft SIP Processing Language (MSPL) message filter to forward basic proxies in a managed SIP application.

SIP forwarding proxy behavior

The following illustration shows the basic flow of a forwarding proxy.

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.

The Request forwarding process starts by starting a single branch with a call to ServerTransaction.CreateBranch. After that, 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 responses have been received for the forwarded request, the object space that contains the ServerTransaction instance and its sole branch is automatically disposed of by the server agent, unless the ServerTransaction.Close() method on ServerTransaction is specifically overridden and contains post-transaction directives.

See also

Other resources

Managed SIP Application API

Learn the basics of Lync Server 2013 SDK