Problem using WCF and NetNamedPipeBinding for IPC

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 be doing wrong?

Answer 1

1 min is the standard wcf timeout.

Do you have a circular reference?

Also, why do you have 2 contracts, when you make a call to client.init who is listening?

Answer 2

Turn on E2E tracing for WCF to check what exactly is timing out. - http://msdn.microsoft.com/en-us/library/ms733025.aspx. Besides your methods might be causing a deadlock since init might require log and log might require init to happen first or something like that.

Answer 3

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