How Do I...? Common Tasks QuickStart Tutorial

How Do I...Create a Remote Object as a Singleton?

This example demonstrates how to modify the Client/Server example by deploying the remote object as a singleton. The client starts two threads and calls the CountMe method on the server on two different channels: TCP and HTTP.

Although this example is very simple, it does illustrate a few important concepts.

• The HelloServer object is only activated once and its destructor is never called.

• When you run the client, thread number two appears to outperform thread number one. The second thread is indeed faster than the first since thread one uses the HTTP channel that transports data in XML using SOAP while TCP uses a binary transport. While TCP clearly outperforms HTTP, the latter is more general and should be used when communicating with unknown endpoints.

• The server object is locked while the counter is incremented in the CountMe call.

• Notice that the count returned by the server is not reset between different invocations of the client. This behavior demonstrates that the server does preserve its state during its lifetime.

• Each client thread makes a call to the server and then yields control to its partner to ensure they both get a chance to run.

• Each thread registers its own channel and connects to the server using different URIs. These are "http://localhost:8086/SayHello" for thread one and "tcp://localhost:8085/SayHello" for thread two.

• The client executable waits for both threads to finish before terminating.

NOTE:  Do not specify a port number when registering the client channels. The framework uses the port number on the channels to determine if the channel should listen or connect. When the channel is registered with a port number, the channel listens. If the port number is zero, it attempts to connect to a remote channel at the specified URI.

VB Singleton Sample