Question

I’m trying to learn WCF to use it as an IPC mechanism for a host/plugin system. The host needs to be able to call the plugin to Start/Stop it, and the plugin needs to call the server back to perform logging.

I made a simple test case where the host creates an endpoint on net.pipe://localhost/SampleServer with the following ServiceContract:

[ServiceContract]
public interface IWcfServer
{
    [OperationContract]
    void Log(string message);
}

And the plugin creates an endpoint on net.pipe://localhost/SampleClient with the following ServiceContract:

[ServiceContract]
public interface IWcfClient
{
    [OperationContract]
    string Init();
}

Here’s a sample of how I’m setting up each endpoint:

this.server = new ServiceHost(this);
this.server.AddServiceEndpoint(typeof(IWcfServer), 
                               new NetNamedPipeBinding(), 
                               "net.pipe://localhost/SampleServer");
this.server.Open();

And here’s a sample of how I’m making the calls:

ChannelFactory<IWcfClient> factory = new ChannelFactory<IWcfClient>(
                            new NetNamedPipeBinding(),
                            new EndpointAddress("net.pipe://localhost/SampleClient"));
IWcfClient client = factory.CreateChannel();
using ((IClientChannel)client)
{
    client.Init());
}

I already confirmed that the host can call plugin.Init(), and the plugin can call host.Log(message) without issues. However, if this following scenario happens:

1. Host calls plugin.Init()
2. During the execution of plugin.Init(), the plugin attempts to call host.Log(message)

The applications freezes, and I get a TimeoutException after 1min. Anyone has any ideas on what I’m doing wrong?

Answer 1

what is the InstanceContextMode of the service host ? If it is a singleton, it will block until Init() returns – resulting in a circular dependency.