see also "WCF push to client through firewall"

I need to have a WCF client that connect to a WCF server, then when some of the data changes on the server the clients need to update its display.

As there is likely to be a firewall between the clients and the server.

• All communications must be over HTTP
• The server can not make an (physical) outgoing call to the client.

As I am writing both the client and the server I do not need to limit the solution to only using soap etc.

I am looking for built in surport for "long polling" / "Comet" etc

Thanks for the most informative answer from Drew Marsh on how to implement long polling in WCF. However I thought the main “selling point” of WCF was that you could do this sort of thing just by configuring the channels to be used in the config file. E.g I want a channel that logically two way but physically incoming only.