In my client/server applications, I want a single duplex WCF channel to be available for communication with its server - sort of a background connection that isn't strictly necessary for the client application to run, but is desirable for reporting status to the server. I have a Ping() call and Echo() callback in the IServerContract and IClientContract respectively.
I implement class ServerProxy : System.ServiceModel.DuplexClientBase<IServerContract> with the pass-thru methods to base.InnerChannel.
If I create var proxy = new ServerProxy(...) in my client, I can just begin calling proxy.Ping() and WCF will automatically open the connection for the first call and perform the operation call immediately after. However, the first call always takes ~10 seconds because of channel initialization and authentication. (I'm using windows authentication, Message-based security, EncryptAndSign.) Subsequent calls are quicker.
I believe this 10 seconds is unavoidable, but there is usually time prior to the first call by the client to the server during which this initialization could happen. So rather than wait for the auto-open feature of DuplexClientBase, I open the channel early with a call to proxy.InnerDuplexChannel.Open(). (proxy.Open() throws an exception and this indirection seems to avoid it.)
Unfortunately, authenticating the client-to-server channel does not also authenticate the server-to-client callback channel. Instead, the first call by the server to the client ALSO requires ~10 seconds. Since I'm using netTcp binding I'm surprised by this, but I'll assume it is to be expected for now.
How can I open the callback channel preemptively as well?
I could require the client to call some Login() method instead, but I don't believe that WCF should strictly require an operation before user-code can be aware of a connected client!
Hint(?): I imagine that this code would have to go in a place in the WCF pipeline/lifecycle where the server has the opportunity to perform custom actions upon a client-connected event (and BEFORE any operation message is transmitted). This integration point has so far eluded me.
