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Remoting Example: CallContext

This sample uses the CallContext class and the ILogicalThreadAffinative interface to pass information between threads on either end of a call across an application domain boundary or a context boundary.

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.

Although this sample does not compile ServiceClass.vb, it is included here to demonstrate implementing ILogicalThreadAffinative.

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 this sample

  • Type the following commands at the command prompt:

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

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

    vbc /r:System.Runtime.Remoting.dll /r:ServiceClass.dll clientvb.vb

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

ServiceClass.cs

using System;
using System.Collections;
using System.Diagnostics;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Contexts;
using System.Runtime.Remoting.Channels;

public class ContextBoundType : ContextBoundObject{

    private DateTime starttime;

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

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

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

        // This call overwrites the client's 
        // CallContextString.
        CallContext.SetData("ServerThreadData", new CallContextString("This is the server side replacement."));
      return DateTime.Now;
   }

}

//  One method of communicating between client and server is 
//  to use the CallContext. Calling CallContext essentially puts the data
//  in a Thread Local Store. This means that the information is available 
//  to that thread or that "logical" thread (across application domains) only.
[Serializable]
public class CallContextString : ILogicalThreadAffinative{

    String _str ="";
    public CallContextString(String str){
      _str = str;
      Console.WriteLine("CallContextString created.");
    }

    public override String ToString(){
      return _str;
    }
}

ServiceClass.vb

This file is included for documentation purposes only.

Imports System
Imports System.Collections
Imports System.Diagnostics
Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Messaging
Imports System.Runtime.Remoting.Contexts
Imports System.Runtime.Remoting.Channels

Public Class ContextBoundType
   Inherits ContextBoundObject

   Private StartTime As DateTime

   Public Sub New()
      Console.WriteLine("A ContextBoundType instance has been created. (Constructor)")
      StartTime = DateTime.Now
   End Sub  'New

   Protected Overrides Sub Finalize()
      Console.WriteLine("ContextBoundType being collected after " & (New TimeSpan(DateTime.Now.Ticks - starttime.Ticks)).ToString() & " seconds.")
      MyBase.Finalize()
   End Sub   'Finalize

   Public Function GetServerTime() As DateTime
      Console.WriteLine("Time requested by a client.")

      ' This call overwrites the client's 
      ' CallContextString.
      CallContext.SetData("ServerThreadData", New CallContextString("This is the server side replacement."))

      Return DateTime.Now

   End Function  'GetServerTime

End Class 'ContextBoundType


'  One of the methods of communicating between client and server is 
'  to use the CallContext. Calling CallContext essentially puts the data
'  in a Thread Local Store. This means that the information is available 
'  to that thread or that "logical" thread (across application domains) only.
<Serializable> _
Public Class CallContextString
   Implements ILogicalThreadAffinative

   Private _str As String = ""

   Public Sub New(ByVal Contents As String)
      _str = Contents
      Console.WriteLine("CallContextString created with string ""{0}""", Contents)
   End Sub  'New

   Public Overrides Function ToString() As String
      Return _str
   End Function  'ToString

End Class 'CallContextString

ClientVB.vb

Imports System
Imports System.Reflection
Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Channels
Imports System.Runtime.Remoting.Channels.Tcp
Imports System.Runtime.Remoting.Channels.Http
Imports System.Runtime.Remoting.Contexts
Imports System.Runtime.Remoting.Messaging

Public Class ClientProcess
   <MTAThread()> _
   Public Shared Sub Main()

      Dim Channel As New HttpChannel()
      ChannelServices.RegisterChannel(Channel)

      Dim RemoteType As New WellKnownClientTypeEntry(GetType(ContextBoundType), "http://localhost:8080/TcpCBOService")
      RemotingConfiguration.RegisterWellKnownClientType(RemoteType)

      ' This sets a CallContextDataSlot on this thread. CallContextString      
      ' will convert the ThreadLocalDataStore into a property on the 
      ' message, which will then be merged into the ThreadLocalDataStore 
      ' on the server. This is a nice way to pass information from client 
      ' to server threads and back again. NOTE: This data store has 
      ' logical thread scope. If an application domain has more than one 
      ' thread making calls, each thread will have its own logical 
      ' CallContext, and the server thread will keep each separate.
      CallContext.SetData("ServerThreadData", New CallContextString("This is the thread data inserted on the client thread."))

      Console.WriteLine("CallContextString prior to the call: " & CallContext.GetData("ServerThreadData").ToString())

      Dim service As New ContextBoundType()

      Console.WriteLine("Server time is: " & service.GetServerTime().ToLongTimeString())

      Console.WriteLine("CallContextString after the call: " & CallContext.GetData("ServerThreadData").ToString())

   End Sub   'Main

End Class   'ClientProcess

Client.cs

using System;
using System.Reflection;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Tcp;
using System.Runtime.Remoting.Channels.Http;
using System.Runtime.Remoting.Contexts;
using System.Runtime.Remoting.Messaging;

public class ClientProcess{

   public static void Main(string[] Args){

        HttpChannel channel = new HttpChannel();
        ChannelServices.RegisterChannel(channel);

        WellKnownClientTypeEntry remotetype = new WellKnownClientTypeEntry(typeof(ContextBoundType),"http://localhost:8080/TcpCBOService");
       RemotingConfiguration.RegisterWellKnownClientType(remotetype);

        // This sets a CallContextDataSlot on this thread. 
        // CallContextString will convert the ThreadLocalDataStore into 
        // a property on the message, which will then be merged into the 
        // ThreadLocalDataStore on the server. This is a nice way to pass 
        // information from client to server threads and back again. 
        // NOTE: This data store has logical thread scope. If an 
        // application domain has more than one thread making calls, 
        // each thread will have its own logical CallContext, and the 
        // server thread will keep each separate.
        CallContext.SetData("ServerThreadData", new CallContextString("This is the thread data inserted on the client thread."));

        Console.WriteLine("CallContextString prior to the call: " + CallContext.GetData("ServerThreadData").ToString());

        ContextBoundType service = new ContextBoundType(); 

        Console.WriteLine("Server time is: " + service.GetServerTime().ToLongTimeString());

        Console.WriteLine("CallContextString after the call: " + CallContext.GetData("ServerThreadData").ToString());

   }
}

Server.cs

using System;
using System.Diagnostics;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Tcp;
using System.Runtime.Remoting.Channels.Http;
using System.Runtime.Remoting.Contexts;
using System.Runtime.Remoting.Messaging;
using System.Threading;

public class ServerProcess{

   public static void Main(string[] Args){

      HttpChannel channel = new HttpChannel(8080);

      ChannelServices.RegisterChannel(channel);
        
      WellKnownServiceTypeEntry WKSTE = new WellKnownServiceTypeEntry(typeof(ContextBoundType),"TcpCBOService", WellKnownObjectMode.SingleCall);
      RemotingConfiguration.RegisterWellKnownServiceType(WKSTE);

      Console.WriteLine("Press enter to stop this process.");
      Console.ReadLine();

   }

}

See Also

Remoting Examples | CallContext | ILogicalThreadAffinative

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