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Remoting Example: Tracking Service

This topic is specific to a legacy technology that is retained for backward compatibility with existing applications and is not recommended for new development. Distributed applications should now be developed using the  Windows Communication Foundation (WCF).

The TrackingServices class provides for a general tracking service with pluggable tracking handlers. Methods on the ITrackingHandler interface are called under the following circumstances:

  • An ObjRef object has been generated (as the result of a marshal).

  • An ObjRef has been received (as the result of an unmarshal).

  • An object has been disconnected.

For more details, see TrackingServices and ITrackingHandler in the reference documentation.

3tzky0f2.Caution(en-us,VS.100).gifCaution:
.NET Framework 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 Framework 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. Copy all files into one directory.

  2. Type the following commands at a command prompt:

    vbc /t:library /r:System.Runtime.Remoting.dll TrackingHandler.vb
    vbc /t:library /r:System.Runtime.Remoting.dll RemoteType.vb
    vbc /r:RemoteType.dll /r:System.Runtime.Remoting.dll /r:TrackingHandler.dll server.vb
    vbc /r:RemoteType.dll /r:System.Runtime.Remoting.dll client.vb
    
  3. Open two command prompts pointing to the same directory. In one, type server. In the other, type client.

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.

TrackingHandler

Imports System
Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Channels
Imports System.Runtime.Remoting.Services

Public Class TrackingHandler
    Implements ITrackingHandler

    ' Notifies a handler that an object has been marshaled.
    Public Sub MarshaledObject(ByVal obj As Object, ByVal objref As System.Runtime.Remoting.ObjRef) Implements System.Runtime.Remoting.Services.ITrackingHandler.MarshaledObject
        Console.WriteLine("Tracking: An instance of {0} was marshaled. The instance HashCode is: {1}", _
            obj.ToString(), obj.GetHashCode().ToString())
        Console.WriteLine("ObjRef dump:")
        If (objref.ChannelInfo IsNot Nothing) Then
            Console.WriteLine("  -- ChannelInfo: ")
            DumpChannelInfo(objref.ChannelInfo)
        End If

        If (objref.EnvoyInfo IsNot Nothing) Then
            Console.WriteLine("  -- EnvoyInfo: " + CType(objref.EnvoyInfo, Object).ToString())
        End If
        If (objref.TypeInfo IsNot Nothing) Then
            Console.WriteLine("  -- TypeInfo: " + CType(objref.TypeInfo, Object).ToString())
            Console.WriteLine("      -- " + objref.TypeInfo.TypeName)
        End If
        If (objref.URI IsNot Nothing) Then
            Console.WriteLine("  -- URI: " + objref.URI.ToString())
        End If
    End Sub

    Private Sub DumpChannelInfo(ByVal info As IChannelInfo)
        Dim obj As Object
        For Each obj In info.ChannelData
            If (obj Is GetType(ChannelDataStore)) Then
                Dim uri As String
                For Each uri In CType(obj, ChannelDataStore).ChannelUris
                    Console.WriteLine("      -- ChannelUris:" + uri)
                Next
            End If
        Next

    End Sub

    ' Notifies a handler that an object has been unmarshaled.
    Public Sub UnmarshaledObject(ByVal obj As Object, ByVal [or] As System.Runtime.Remoting.ObjRef) Implements System.Runtime.Remoting.Services.ITrackingHandler.UnmarshaledObject
        Console.WriteLine("Tracking: An instance of {0} was unmarshaled. The instance HashCode is: {1}", obj.ToString(), obj.GetHashCode().ToString())
    End Sub

    ' Notifies a handler that an object has been disconnected.
    Public Sub DisconnectedObject(ByVal obj As Object) Implements System.Runtime.Remoting.Services.ITrackingHandler.DisconnectedObject
        Console.WriteLine("Tracking: An instance of {0} was disconnected. The instance HashCode is: {1}", obj.ToString(), obj.GetHashCode().ToString())
    End Sub
End Class

RemoteType

Imports System

Public Class ServiceClass
    Inherits MarshalByRefObject

    Private starttime As DateTime

    Public Sub New()
        Console.WriteLine("A ServiceClass has been created.")
        starttime = DateTime.Now
    End Sub

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

    Public Function GetServerTime() As DateTime
        Console.WriteLine("Time requested by client")
        Return DateTime.Now
    End Function
End Class

Server

[Visual Basic]

Imports System
Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Channels
Imports System.Runtime.Remoting.Channels.Tcp
Imports System.Runtime.Remoting.Services
Imports TrackingHandler

Public Class Server
    Public Shared Sub Main()
        Dim channel As TcpChannel = New TcpChannel(8080)
        ChannelServices.RegisterChannel(channel, False)

        TrackingServices.RegisterTrackingHandler(New TrackingHandler())

        Dim service As ServiceClass = New ServiceClass()
        Dim obj As ObjRef = RemotingServices.Marshal(service, "TcpService")

        Console.WriteLine("Press Enter to unmarshal the object.")
        Console.ReadLine()

        RemotingServices.Unmarshal(obj)

        Console.WriteLine("Press Enter to disconnect the object.")
        Console.ReadLine()

        RemotingServices.Disconnect(service)
    End Sub
End Class

[C#]

using System;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Tcp;
using System.Runtime.Remoting.Services;
using TrackingHandler;
using RemoteType;

namespace Server
{
    public class Server
    {
        public static void Main(string[] Args)
        {
            TcpChannel channel = new TcpChannel(8080);
            ChannelServices.RegisterChannel(channel, false);

            TrackingServices.RegisterTrackingHandler(new TrackingHandler.TrackingHandler());

            ServiceClass service = new ServiceClass();
            ObjRef obj = RemotingServices.Marshal(service, "TcpService");

            Console.WriteLine("\r\nPress Enter to unmarshal the object.");
            Console.ReadLine();

            RemotingServices.Unmarshal(obj);

            Console.WriteLine("Press Enter to disconnect the object.");
            Console.ReadLine();

            RemotingServices.Disconnect(service);
        }
    }
}

Client

Imports System
Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Channels
Imports System.Runtime.Remoting.Channels.Tcp

Public Class Client

    Public Shared Sub Main()
        ChannelServices.RegisterChannel(New TcpChannel(), False)

        Dim remotetype As WellKnownClientTypeEntry = New WellKnownClientTypeEntry( _
            GetType(ServiceClass), _
            "tcp://localhost:8080/TcpService")
        RemotingConfiguration.RegisterWellKnownClientType(remotetype)

        Dim service As ServiceClass = New ServiceClass()
        Console.WriteLine("Server time is: " & service.GetServerTime().ToLongTimeString())
    End Sub

End Class

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