Two-Way Communication

Article
09/15/2021

The Two-Way sample demonstrates how to perform transacted two-way queued communication over MSMQ. This sample uses the netMsmqBinding binding. In this case, the service is a self-hosted console application that allows you to observe the service receiving queued messages.

Note

The setup procedure and build instructions for this sample are located at the end of this topic.

This sample is based on the Transacted MSMQ Binding.

In queued communication, the client communicates to the service using a queue. The client sends messages to a queue, and the service receives messages from the queue. The service and client therefore, do not have to be running at the same time to communicate using a queue.

This sample demonstrates 2-way communication using queues. The client sends purchase orders to the queue from within the scope of a transaction. The service receives the orders, processes the order and then calls back the client with the status of the order from the queue within the scope of a transaction. To facilitate two-way communication the client and service both use queues to enqueue purchase orders and order status.

The service contract IOrderProcessor defines one-way service operations that suit the use of queuing. The service operation includes the reply endpoint to use to send the order statuses to. The reply endpoint is the URI of the queue to send the order status back to the client. The order processing application implements this contract.

[ServiceContract(Namespace="http://Microsoft.ServiceModel.Samples")]
public interface IOrderProcessor
{
    [OperationContract(IsOneWay = true)]
    void SubmitPurchaseOrder(PurchaseOrder po, string
                                  reportOrderStatusTo);
}

The reply contract to send order status is specified by the client. The client implements the order status contract. The service uses the generated proxy of this contract to send order status back to the client.

[ServiceContract]
public interface IOrderStatus
{
    [OperationContract(IsOneWay = true)]
    void OrderStatus(string poNumber, string status);
}

The service operation processes the submitted purchase order. The OperationBehaviorAttribute is applied to the service operation to specify automatic enlistment in a transaction that is used to receive the message from the queue and automatic completion of transactions on completion of the service operation. The Orders class encapsulates order processing functionality. In this case, it adds the purchase order to a dictionary. The transaction that the service operation enlisted in is available to the operations in the Orders class.

The service operation, in addition to processing the submitted purchase order, replies back to the client on the status of the order.

[OperationBehavior(TransactionScopeRequired = true, TransactionAutoComplete = true)]
public void SubmitPurchaseOrder(PurchaseOrder po, string reportOrderStatusTo)
{
    Orders.Add(po);
    Console.WriteLine("Processing {0} ", po);
    Console.WriteLine("Sending back order status information");
    NetMsmqBinding msmqCallbackBinding = new NetMsmqBinding("ClientCallbackBinding");
    OrderStatusClient client = new OrderStatusClient(msmqCallbackBinding, new EndpointAddress(reportOrderStatusTo));

    // Please note that the same transaction that is used to dequeue the purchase order is used
    // to send back order status.
    using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required))
    {
        client.OrderStatus(po.PONumber, po.Status);
        scope.Complete();
    }
    //Close the client.
    client.Close();
}

The MSMQ queue name is specified in an appSettings section of the configuration file. The endpoint for the service is defined in the System.ServiceModel section of the configuration file.

Note

The MSMQ queue name and endpoint address use slightly different addressing conventions. The MSMQ queue name uses a dot (.) for the local machine and backslash separators in its path. The Windows Communication Foundation (WCF) endpoint address specifies a net.msmq: scheme, uses "localhost" for the local machine, and uses forward slashes in its path. To read from a queue that is hosted on the remote machine, replace the "." and "localhost" to the remote machine name.

The service is self hosted. When using the MSMQ transport, the queue used must be created in advance. This can be done manually or through code. In this sample, the service checks for the existence of the queue and creates it, if necessary. The queue name is read from the configuration file. The base address is used by the ServiceModel Metadata Utility Tool (Svcutil.exe) to generate the proxy to the service.

// Host the service within this EXE console application.
public static void Main()
{
    // Get MSMQ queue name from appSettings in configuration.
    string queueName = ConfigurationManager.AppSettings["queueName"];

    // Create the transacted MSMQ queue if necessary.
    if (!MessageQueue.Exists(queueName))
        MessageQueue.Create(queueName, true);

    // Create a ServiceHost for the OrderProcessorService type.
    using (ServiceHost serviceHost = new ServiceHost(typeof(OrderProcessorService)))
    {
        // Open the ServiceHost to create listeners and start listening for messages.
        serviceHost.Open();

        // The service can now be accessed.
        Console.WriteLine("The service is ready.");
        Console.WriteLine("Press <ENTER> to terminate service.");
        Console.WriteLine();
        Console.ReadLine();
    }
}

The client creates a transaction. Communication with the queue takes place within the scope of the transaction, causing it to be treated as an atomic unit where all messages succeed or fail.

// Create a ServiceHost for the OrderStatus service type.
using (ServiceHost serviceHost = new ServiceHost(typeof(OrderStatusService)))
{

    // Open the ServiceHostBase to create listeners and start listening for order status messages.
    serviceHost.Open();

    // Create the purchase order.
    ...

    // Create a client with given client endpoint configuration.
    OrderProcessorClient client = new OrderProcessorClient("OrderProcessorEndpoint");

    //Create a transaction scope.
    using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required))
    {
        string hostName = Dns.GetHostName();

        // Make a queued call to submit the purchase order.
        client.SubmitPurchaseOrder(po, "net.msmq://" + hostName + "/private/ServiceModelSamplesTwo-way/OrderStatus");

        // Complete the transaction.
        scope.Complete();
    }

    //Close down the client.
    client.Close();

    Console.WriteLine();
    Console.WriteLine("Press <ENTER> to terminate client.");
    Console.ReadLine();

    // Close the ServiceHost to shutdown the service.
    serviceHost.Close();
}

The client code implements the IOrderStatus contract to receive order status from the service. In this case, it prints out the order status.

[ServiceBehavior]
public class OrderStatusService : IOrderStatus
{
    [OperationBehavior(TransactionAutoComplete = true,
                        TransactionScopeRequired = true)]
    public void OrderStatus(string poNumber, string status)
    {
        Console.WriteLine("Status of order {0}:{1} ", poNumber ,
                                                           status);
    }
}

The order status queue is created in the Main method. The client configuration includes the order status service configuration to host the order status service, as shown in the following sample configuration.

<appSettings>
  <!-- Use appSetting to configure MSMQ queue name. -->
  <add key="queueName" value=".\private$\ServiceModelSamplesTwo-way/OrderStatus" />
</appSettings>

<system.serviceModel>

  <services>
    <service
       name="Microsoft.ServiceModel.Samples.OrderStatusService">
      <!-- Define NetMsmqEndpoint -->
      <endpoint address="net.msmq://localhost/private/ServiceModelSamplesTwo-way/OrderStatus"
                binding="netMsmqBinding"
                contract="Microsoft.ServiceModel.Samples.IOrderStatus" />
    </service>
  </services>

  <client>
    <!-- Define NetMsmqEndpoint -->
    <endpoint name="OrderProcessorEndpoint"
              address="net.msmq://localhost/private/ServiceModelSamplesTwo-way/OrderProcessor"
              binding="netMsmqBinding"
              contract="Microsoft.ServiceModel.Samples.IOrderProcessor" />
  </client>

</system.serviceModel>

When you run the sample, the client and service activities are displayed in both the service and client console windows. You can see the service receive messages from the client. Press ENTER in each console window to shut down the service and client.

The service displays the purchase order information and indicates it is sending back the order status to the order status queue.

The service is ready.
Press <ENTER> to terminate service.

Processing Purchase Order: 124a1f69-3699-4b16-9bcc-43147a8756fc
        Customer: somecustomer.com
        OrderDetails
                Order LineItem: 54 of Blue Widget @unit price: $29.99
                Order LineItem: 890 of Red Widget @unit price: $45.89
        Total cost of this order: $42461.56
        Order status: Pending

Sending back order status information

The client displays the order status information sent by the service.

Press <ENTER> to terminate client.
Status of order 124a1f69-3699-4b16-9bcc-43147a8756fc:Pending

To set up, build, and run the sample

Ensure that you have performed the One-Time Setup Procedure for the Windows Communication Foundation Samples.
To build the C# or Visual Basic .NET edition of the solution, follow the instructions in Building the Windows Communication Foundation Samples.
To run the sample in a single- or cross-machine configuration, follow the instructions in Running the Windows Communication Foundation Samples.

Note

If you use Svcutil.exe to regenerate the configuration for this sample, be sure to modify the endpoint names in the client configuration to match the client code.

By default with the NetMsmqBinding, transport security is enabled. There are two relevant properties for MSMQ transport security, MsmqAuthenticationMode and MsmqProtectionLevel. By default, the authentication mode is set to Windows and the protection level is set to Sign. For MSMQ to provide the authentication and signing feature, it must be part of a domain and the active directory integration option for MSMQ must be installed. If you run this sample on a computer that does not satisfy these criteria you receive an error.

To run the sample on a computer joined to a workgroup or without active directory integration

If your computer is not part of a domain or does not have active directory integration installed, turn off transport security by setting the authentication mode and protection level to None as shown in the following sample configuration:

<configuration>

  <appSettings>
    <!-- Use appSetting to configure MSMQ queue name. -->
    <add key="queueName" value=".\private$\ServiceModelSamplesTwo-way/OrderProcessor" />
  </appSettings>

  <system.serviceModel>
    <services>
      <service
          name="Microsoft.ServiceModel.Samples.OrderProcessorService">
        <!-- Define NetMsmqEndpoint -->
        <endpoint address="net.msmq://localhost/private/ServiceModelSamplesTwo-way/OrderProcessor"
                  binding="netMsmqBinding"
                  bindingConfiguration="TransactedBinding"
                  contract="Microsoft.ServiceModel.Samples.IOrderProcessor" />
      </service>
    </services>

    <bindings>
      <netMsmqBinding>
        <binding name="TransactedBinding" >
         <security mode="None" />
        </binding>
      </netMsmqBinding>
    </bindings>

  </system.serviceModel>

</configuration>

Turning off security for a client configuration generates the following:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <!-- Use appSetting to configure MSMQ queue name. -->
    <add key="queueName" value=".\private$\ServiceModelSamplesTwo-way/OrderStatus" />
  </appSettings>

  <system.serviceModel>

    <services>
      <service
         name="Microsoft.ServiceModel.Samples.OrderStatusService">
        <!-- Define NetMsmqEndpoint -->
        <endpoint address="net.msmq://localhost/private/ServiceModelSamplesTwo-way/OrderStatus"
                  binding="netMsmqBinding"
                  bindingConfiguration="TransactedBinding" contract="Microsoft.ServiceModel.Samples.IOrderStatus" />
      </service>
    </services>

    <client>
      <!-- Define NetMsmqEndpoint -->
      <endpoint name="OrderProcessorEndpoint"
                address="net.msmq://localhost/private/ServiceModelSamplesTwo-way/OrderProcessor"
                binding="netMsmqBinding"
                bindingConfiguration="TransactedBinding"
                contract="Microsoft.ServiceModel.Samples.IOrderProcessor" />
    </client>

    <bindings>
      <netMsmqBinding>
        <binding name="TransactedBinding" >
         <security mode="None" />
        </binding>
      </netMsmqBinding>
    </bindings>

  </system.serviceModel>

</configuration>

The service for this sample creates a binding in the OrderProcessorService. Add a line of code after the binding is instantiated to set the security mode to None.
```
NetMsmqBinding msmqCallbackBinding = new NetMsmqBinding();
msmqCallbackBinding.Security.Mode = NetMsmqSecurityMode.None;
```
Ensure that you change the configuration on both the server and the client before you run the sample.

Note

Setting security mode to None is equivalent to setting MsmqAuthenticationMode, MsmqProtectionLevel or Message security to None.

Share via

Two-Way Communication

To set up, build, and run the sample

To run the sample on a computer joined to a workgroup or without active directory integration

Additional resources