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Remoting Example: Channel Sink Provider

This code example builds a ChannelSinkPropertySetterProvider, which is a channel sink provider that can read values in the application configuration file and walk the sink stack looking for channel sinks that support the properties it found in that file. This can be a useful way to build a sink chain using the configuration file rather than creating the chain programmatically and passing IDictionary objects to the constructors.

This provider does not insert any sink into the channel sink chain. It merely walks the sink chain looking for compatible properties and can easily be customized to take only those properties supported by a specific sink.

In addition, this sample provider is written and compiles in Visual Basic, while the remainder of the infrastructure is written in C#. A C# version of the provider is also included for information purposes, but are not compiled by the command lines given..

CAUTION   .NET remoting does not do authentication or encryption by default. Therefore, it is recommended that you take all necessary steps to make certain of the identity of clients or servers before interacting with them remotely. Because .NET remoting applications require FullTrust permissions to execute, if a unauthorized client were granted access on your server, the client could execute code as though it were fully trusted. Always authenticate your endpoints and encrypt the communication streams, either by hosting your remoted types in Internet Information Services (IIS) or by building a custom channel sink pair to do this work.

To compile and run this sample

  1. Type the following commands at the command prompt:

    vbc -r:System.Runtime.Remoting.dll -t:library /out:PropsSink.dll ChannelSinkPropertySetterProvider.vb

    csc /r:System.Runtime.Remoting.dll /t:library /out:ServiceClass.dll serviceclass.cs

    csc /r:System.Runtime.Remoting.dll /r:ServiceClass.dll /r:PropsSink.dll client.cs

    csc /r:System.Runtime.Remoting.dll /r:ServiceClass.dll server.cs

  2. Open two command prompts pointing to the same directory. In one, type server. Once that is running, type client at the other command prompt.

This channel sink provider supports the writeToConsole attribute to indicate whether you want a console dump of the provider's activities in the client console. For this sample, the attribute is set to true.

This application runs on a single computer or across a network. If you want to run this application over a network, you must replace "localhost" in the client configuration with the name of the remote computer.

ChannelSinkPropertySetterProvider.vb

ChannelSinkPropertySetterProvider.cs

This file is included for information only.

using System;
using System.Collections;
using System.IO;
using System.Reflection;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Http;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.MetadataServices;

// This class implements a client-side channel sink provider that
// walks the channel sink chain, looking for channel sink
// properties that match those specified in the configuration file. If it 
// finds them, the provider sets them to the values specified in the 
// configuration file. This is a simple helper provider that returns no 
// channel itself. Instead, it merely returns the next channel sink it can // find, or null.
public class ChannelSinkPropertySetterProvider : IClientChannelSinkProvider{

   private IClientChannelSinkProvider _next = null;
   private IDictionary _channelSinkProperties = null;
   private ICollection _providerData = null;

   // Set the writeToConsole attribute on this provider element in the 
   // configuration file to "true"; otherwise, information is not written to the console.
   private bool _consoleDump = false;

   // Default constructor.
   public ChannelSinkPropertySetterProvider(){
      Console.WriteLine("Default constructor called.");

   } // ChannelSinkPropertySetterProvider.

   // Constructor with properties. If writeToConsole attribute is "true", 
   // this constructor will dump all custom configuration properties set 
   // in the configuration file. 

   public ChannelSinkPropertySetterProvider(IDictionary properties, ICollection providerData){

      _channelSinkProperties = properties;

      // Sets the private console dump property for this provider.
      if (properties["writeToConsole"] != null)
         _consoleDump = Boolean.Parse(properties["writeToConsole"].ToString());

      _providerData = providerData;

      if (_consoleDump){
         Console.WriteLine("ChannelSinkPropertySetterProvider custom constructor called.");

         foreach(SinkProviderData sinkData in providerData){

            Console.WriteLine("SinkProvider element: " + sinkData.Name);
            foreach(DictionaryEntry prop in sinkData.Properties){
               Console.WriteLine("Prop name: " + prop.Key.ToString() + " value: " + prop.Value.ToString());
            }

            foreach(object child in sinkData.Children){
               Console.WriteLine("Child: " + child.GetType().Name);
            }
         }
   
         foreach (DictionaryEntry entry in properties){
            Console.WriteLine("channel sink properties: " + entry.Key.ToString() + ", " + entry.Value.ToString());
         }

         Console.WriteLine();
      }

   } // ChannelSinkPropertySetterProvider.


   // Called by the channel. Normally, this method takes any other sinks 
   // created by other providers in the chain, links them together, and 
   // then returns its own sink to the channel. In this case, this
   // provider merely sets matching properties on each channel sink in the 
   // chain, and then returns the **next** channel sink to the channel or 
   // returns null, indicating to the channel that it is the end of the 
   // custom channel sink chain.
   public IClientChannelSink CreateSink(IChannelSender channel, string url, object remoteChannelData){
         
      if (_consoleDump){
         Console.WriteLine("CreateSink is called.");
         Console.WriteLine("By " + channel.GetType().Name);
      }

      IClientChannelSink nextSink = null;

      if (_next != null){

         nextSink = _next.CreateSink(channel, url, remoteChannelData);

         if (nextSink == null){
            if (_consoleDump)
                  Console.WriteLine("Next sink is null!");
            return null;
         }

         WalkSinkChain(nextSink);

      }

      return nextSink;

   }

   // This call walks the sink chain, setting properties as it goes.
   // The channelSinkProperties are the SinkProviderData dictionaries
   // that contain the name of the subnode in the configuration file, and 
   // a dictionary entry of attribute/value entries on that element.

   private void WalkSinkChain(IClientChannelSink thisSink){

      if (thisSink == null)
         return;

      if (_consoleDump)
         Console.WriteLine("\r\n\tWalking the sink chain to find sink properties... \r\n");

      while(thisSink != null){
         if (_consoleDump){
            Console.WriteLine(new String('_',80));
            Console.WriteLine("Next sink is : " + thisSink.GetType().Name);
            DumpSinkProperties(thisSink);
         }
         SetSinkProperties(thisSink);
         thisSink = thisSink.NextChannelSink;
      }

      return;
   }

   private void DumpSinkProperties(IClientChannelSink sink){

      if (sink.Properties == null){
         Console.WriteLine("There are no properties available on the " + sink.GetType().Name + " channelsink.");
         return;
      }

      foreach(DictionaryEntry entry in sink.Properties){
         Console.Write("ChannelSink property: " + entry.Key.ToString() + " value: ");
         if (entry.Value == null)
            Console.WriteLine("No value.");
         else
            Console.WriteLine(entry.Value.ToString());
      }
   
   }

   // This method sets properties on the sink.
   // The algorithm is that in the absence of instance attribute/value 
   // entries, the provider element template attribute/value entries will 
   // be set. This is a simple implementation that does not care about the 
   // element name underneath the provider element.

   private void SetSinkProperties(IClientChannelSink sink){

      if (sink.Properties == null){
         Console.WriteLine("There are no properties available on the " + sink.GetType().Name + " channelsink.");
         return;
      }

      foreach(DictionaryEntry entry in sink.Properties){
         if (_channelSinkProperties.Contains(entry.Key)){

            if (_consoleDump)
               Console.WriteLine("Setting sink property template on " + sink.GetType().Name + "." + entry.Key.ToString());
            sink.Properties[entry.Key] = _channelSinkProperties[entry.Key];
         }
      }

      foreach(SinkProviderData provider in _providerData){
         foreach(DictionaryEntry configEntry in provider.Properties){
            if (sink.Properties.Contains(configEntry.Key))
               if (_consoleDump)
                  Console.WriteLine("Setting Instance override on " + sink.GetType().Name +  "." + configEntry.Key);
               sink.Properties[configEntry.Key] = configEntry.Value;
         }
      }

      if (_consoleDump)
         DumpSinkProperties(sink);
   }
   
   public IClientChannelSinkProvider Next{
      get { 
         return _next; 
      }

      set { 
         _next = value; 
      }
   }

   // This can be called in the constructor in case this provider is 
   // intended to build its own channel sink provider chain. Without 
   // providing such a chain, this provider must be specified in a 
   // configuration file with other providers.
   private IClientChannelSinkProvider CreateDefaultClientProviderChain(){

      IClientChannelSinkProvider chain = new SoapClientFormatterSinkProvider();            
      IClientChannelSinkProvider sink = chain;

      sink.Next = new BinaryClientFormatterSinkProvider();
      sink = sink.Next;

      return chain;
   } // CreateDefaultClientProviderChain.
} // Class ChannelSinkPropertySetterProvider.

Client.cs

using System;
using System.Runtime.Remoting;

public class Client{
   
   public static void Main(string[] Args){
      
      RemotingConfiguration.Configure("Client.exe.config");
      ServiceClass service = new ServiceClass();
        Console.WriteLine(service.GetServerTime());   
   }
}

Server.cs

using System;
using System.Diagnostics;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Tcp;

public class ServerProcess{

   public static void Main(string[] Args){

        RemotingConfiguration.Configure("server.exe.config");
      Console.WriteLine("Press enter to stop this process.");
      Console.ReadLine();
   
   }
}

ServiceClass.cs

using System;
using System.Diagnostics;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;

public class ServiceClass : MarshalByRefObject{

    private DateTime starttime;

   public ServiceClass(){
      Console.WriteLine("A ServiceClass has been created.");
       starttime = DateTime.Now;
   }

    ~ServiceClass(){
        Console.WriteLine("This object is being collected after " + (new TimeSpan(DateTime.Now.Ticks - starttime.Ticks)).ToString() + " seconds.");
    
    }

   public DateTime GetServerTime(){
       Console.WriteLine("Time requested by a client.");
      return DateTime.Now;
   }

}

Client.exe.config

<configuration>
  <system.runtime.remoting>
    <application>
      <client>
         <wellknown 
            type="ServiceClass, ServiceClass"
            url="http://localhost:8080/RemoteObject"
         />
      </client>
      <channels>
         <channel ref="http">
         <clientProviders>
            <formatter ref="soap"/>
            <provider ref="propsetter" username="bob" writeToConsole="true">
               <endpoint allowAutoRedirect="true"/>
               <endpoint preauthenticate="true"/>
               <endpoint url="example.com:9000" password="xyz" />
               <endpoint url="example.com:9001" password="123" />
               <endpoint timeout="10000"/>
               <endpoint url="example.com:*" username="bob2" password="qwerty" domain="hello" />
            </provider>
         </clientProviders>
         </channel>
      </channels>
   </application>
   <channelSinkProviders>
      <clientProviders>
         <provider 
            id="propsetter" 
            type="ChannelSinkPropertySetterProvider, PropsSink" 
         />
      </clientProviders>
   </channelSinkProviders>
   <debug loadTypes="true" />
  </system.runtime.remoting>
</configuration>

Server.exe.config

<configuration>
  <system.runtime.remoting>
    <application>
      <service>
        <wellknown mode="SingleCall" 
           type="ServiceClass, ServiceClass" 
           objectUri="RemoteObject" 
        />
      </service>
      <channels>
        <channel port="8080" ref="http" />
      </channels>
    </application>
  </system.runtime.remoting>
</configuration>

See Also

Remoting Examples | Channels | Sinks and Sink Chains

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