WCF Callback with Multiple Clients

Question

Is it possible to use two different clients that listen on the same WCF callback and force them both to receive the same data without having to do the processing twice?

Answer 1

Not really - at least not directly. What you are describing is very similar to a publish / subscribe template. The WCF service basically serves only one client and one client at a time.

There are ways to do this in WCF 3.5 and better in WCF 4.0 — with or without Windows Azure.NET Services. There are also other tools and support for the publishing / signing template.

Check out things like:

• Implement WCF Publish / Subscribe Model
• Creating a Pub / Sub Message Bus with WCF and MSMQ
• NServiceBus

If you are Google or Bing for "publishing a WCF publication", you will get a lot more hits - but these three should really get started, I think.

Answer 2

In addition to the links posted by @marc_s, you can also view the publication structure of the Juave Lowy Publish / Subscribe Framework, which is shown graphically below.

Publish-Subscribe Framework http://i.msdn.microsoft.com/cc163537.fig07(en-us).gif .

This structure is described in detail in this MSDN article . And you can download the frame source code for free at Lowe's website, IDesign.net .

Using the Pub / Sub Service allows the publisher to publish an event once for a known endpoint. Pub / Sub Service then takes care of posting a notification to subscribers.