Silverlight notification from server to all clients without UDP

I wonder how can I achieve this without UDP, I have a solution using UDP multicast: http://blogs.msdn.co开发者_运维知识库m/b/ncl/archive/2009/11/18/udp-multicast-in-silverlight-4.aspx but since this is for a high profile customer who has an intranet with port TCP 80 and TCP 8080 only enabled this solution is not possible. Yes, the application runs in an intranet environment.

I need a simple example how to send messages to all Silverlight clients over WCF.

I found this solution, but I have no idea how to implement that into Silverlight:

http://idunno.org/archive/2008/05/29/wcf-callbacks-a-beginners-guide.aspx

I'm out of ideas guys, please help.

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Instead of receiving notifications async the Silverlight client should use polling instead. It can poll a WCF service that will fetch the data from a db...

This is the typical solution. Anyway, you have to handle the case in which the Silverlight client wasn't online and then it becomes online and need to know its state...

However, if you still want Silverlight to receive async notifications try searching for 'Full Duplex'. Here are some starting points: http://blog.developers.ba/post/2009/02/25/Silverlight-chat-application-using-WCF-full-duplex.aspx

http://weblogs.asp.net/dwahlin/archive/2008/06/16/pushing-data-to-a-silverlight-client-with-wcf-duplex-service-part-i.aspx

http://hindams.wordpress.com/2010/04/05/wcf-full-duplex-with-a-silverlight-application/