Esempio di configurazione remota: CallContext

  • Articolo

In questo esempio vengono utilizzate la classe CallContext e l'interfaccia ILogicalThreadAffinative per il passaggio di informazioni tra thread su una delle estremità di una chiamata oltre un limite di dominio applicazione o di contesto.

Questa applicazione viene eseguita su un singolo computer o in una rete. Per eseguire l'applicazione in una rete, nella configurazione del client è necessario sostituire hostlocale con il nome del computer remoto.

Benché non preveda la compilazione di ServiceClass.vb, questo esempio è stato incluso per dimostrare l'implementazione di ILogicalThreadAffinative.

Attenzione   .NET Remoting non consente di effettuare l'autenticazione né la crittografia per impostazione predefinita. Si consiglia dunque di eseguire tutte le azioni necessarie per verificare l'identità dei client o dei server prima di interagire con essi in modalità remota. Poiché l'esecuzione delle applicazioni .NET Remoting richiede autorizzazioni FullTrust, qualora a un client non autorizzato venisse concesso l'accesso al server, il client potrebbe eseguire codice come se fosse completamente attendibile. È necessario autenticare sempre gli endpoint e crittografare i flussi di comunicazione mediante l'hosting dei tipi remoti in Internet Information Services (IIS) oppure generando a questo scopo una coppia di sink di canale personalizzata.

Per compilare l'esempio

  • Digitare i seguenti comandi al prompt dei comandi:

    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

Questo file è incluso solo a scopo di documentazione.

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();

   }

}

Vedere anche

Esempi di comunicazione remota | CallContext | ILogicalThreadAffinative