Ejemplo de interacción remota: CallContext

Artículo
04/11/2008

En este ejemplo se usa la clase CallContext y la interfaz ILogicalThreadAffinative para pasar información entre subprocesos en ambos extremos de una llamada más allá de los límites de un dominio de aplicación o de un contexto.

Esta aplicación se ejecuta en un único equipo o a través de una red. Si desea ejecutar esta aplicación a través de una red, debe reemplazar "localhost" en la configuración del cliente con el nombre del equipo remoto.

Aunque en este ejemplo no se compila ServiceClass.vb, se incluye para demostrar la implementación de ILogicalThreadAffinative.

PRECAUCIÓN .NET remoting no autentica ni codifica de manera predeterminada. Por lo tanto, se recomienda que siga todos los procedimientos necesarios para asegurarse de la identidad de los clientes o servidores antes de interactuar con ellos de manera remota. Como las aplicaciones de .NET remoting requieren permisos FullTrust para ejecutarse, si a un cliente no autorizado se le ha concedido acceso en su servidor, el cliente podrá ejecutar código como si fuera de plena confianza. Autentique siempre los extremos y codifique las secuencias de comunicación, ya sea alojando en Servicios de Internet Information Server (IIS) los tipos utilizados de forma remota o generando un par de receptores de canales personalizados para que se hagan cargo de este trabajo.

Para compilar este ejemplo

Escriba los siguientes comandos en el símbolo del sistema:

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

Este archivo se incluye sólo con fines de documentación.

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), "https://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),"https://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();

   }

}

Vea también

Ejemplos de interacción remota | CallContext | ILogicalThreadAffinative

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