How to solve “The ChannelDispatcher is unable to open its IChannelListener” error?

Question

I\'m trying to communicate between WCF hosted in Windows Service and my service GUI. The problem is when I\'m trying to execute OperationContract method I\'m getting

Answer 1

I know you already solved the problem, but nobody pointed out why it solved the problem, and what caused the error. The issue w/ your first code was that your program (class Program) specified an open call to the class that was itself "class Program", in other words, it's RECURSIVE. No wonder it was giving the unable to open the listener error! This was a good one! :-)

Answer 2

maybe the port is already used by another program on your machine, like an antivirus program? Or it's a Windows reserved port. Could you try setting the port to something like 11111?

Answer 3

I encountered this exception for the same reason as the OP but I couldn't move my service's implementation into a new class. So, I found another solution. ServiceHost has a second overload that takes an instance of a service. Thus, here are the changes applied to the OP's 'BAD' code:

namespace WCFServer
{
    [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)] // required
    public class Program : IWCFService
    {
        private ServiceHost host;

        static void Main(string[] args)
        {
            new Program();
        }

        public Program()
        {
            host = new ServiceHost(this); // changed
            host.Open();

            Console.WriteLine("Server Started!");
            Console.ReadKey();
        }

        #region IWCFService Members

        public int CheckHealth(int id)
        {
            return (1);
        }

        #endregion
    }
}

Answer 4

I think this part of the configuration is ignored

<message clientCredentialType="UserName" />

when you set

<security mode = "Transport">

Answer 5

There should be a host.Close() call before calling the service again. Therefore use try, catch and finally block. Close the connection in finally before making second call.

Answer 6

I solved it :D

Here's the explanaition of the problem:

First BAD code:

namespace WCFServer
{
    public class Program : IWCFService
    {
        private ServiceHost host;

        static void Main(string[] args)
        {
            new Program();
        }

        public Program()
        {
            host = new ServiceHost(typeof(Program));

            host.Open();

            Console.WriteLine("Server Started!");

            Console.ReadKey();
        }

        #region IWCFService Members

        public int CheckHealth(int id)
        {
            return (1);
        }

        #endregion
    }
}

As you can see the service contract is implemented in class hosting the service. This caused the whole error thing (maybe typeof() runs a constructor, i don't know I'm open to constructive input in this matter).

The GOOD code:

namespace WCFServer
{
    public class Program
    {
        private ServiceHost host;

        static void Main(string[] args)
        {
            new Program();
        }

        public Program()
        {
            host = new ServiceHost(typeof(WCF));

            host.Open();

            Console.WriteLine("Server Started!");

            Console.ReadKey();
        }
    }

    public class WCF : IWCFService
    {

        #region IWCFService Members

        public int CheckHealth(int id)
        {
            return (1);
        }

        #endregion
    }
}

Service Contract for both files:

[ServiceContract]
public interface IWCFService
{
    [OperationContract]
    int CheckHealth(int id);
}

App.config

<configuration>
<system.serviceModel>
    <behaviors>
        <serviceBehaviors>
            <behavior name="WCFBehavior" />
        </serviceBehaviors>
    </behaviors>
    <bindings>
        <netTcpBinding>
            <binding name="tcpBinding">
                <security>
                    <transport>
                        <extendedProtectionPolicy policyEnforcement="Never" />
                    </transport>
                </security>
            </binding>
        </netTcpBinding>
    </bindings>
    <services>
        <service name="WCFServer.WCF">
            <endpoint address="net.tcp://localhost:1111/TcpIHostMonitor" binding="netTcpBinding"
                bindingConfiguration="tcpBinding" name="netTcpEndpoint" contract="WCFServer.IWCFService" />
        </service>
    </services>
</system.serviceModel>