GetCallbackChannel（）如何在双工wcf通道上工作？

Question

When a service is working with a duplex binding in WCF, you can do this within an operation:

OperationContext.Current.GetCallbackChannel<IClientReceiver>()

to get a reference to the caller. What is that reference? I mean, it looks like it's doing some voo-doo magic. What is happening behind the scenes that allows the service to send a message back to the client?

And how does this work differently on a TCP binding vs. duplex http binding? Because I understand TCP can natively call back to the client, but http can't so it has to create a second channel on the server side to call down to the client.

Answer 1

On the WSDualHttpBinding there are actually two HTTP connections: one from the client to the server, one from the server to the client. GetCallbackChannel<T> will return a reference to a channel which knows how to send messages to the client, and, as you pointed out, is dependent on the underlying transport.