Re: Singleton Objects
From: Ken Kolda (ken.kolda_at_elliemae-nospamplease.com)
Date: 11/01/04
- Next message: Petr Votocek: "format of binary serialized data..."
- Previous message: Ken Kolda: "Re: Singleton Objects"
- In reply to: pSm: "Re: Singleton Objects"
- Next in thread: pSm: "Re: Singleton Objects"
- Reply: pSm: "Re: Singleton Objects"
- Messages sorted by: [ date ] [ thread ]
Date: Mon, 1 Nov 2004 15:04:47 -0800
By the way, I should also mention a couple of other issues:
1) Your code isn't thread-safe. You need to implement some locking on your
server to ensure no two clients are setting the message at the same time (or
attempting to receive the message while it's being set).
2) You have your lastid and message fields on the cldRemoteType as Shared. I
don't see any reason from the code you've provided why you would want these
fields as shared instead of instance fields. Using shared fields will just
increase the likelihood of modifying them elsewhere in a non-thread-safe
manner.
Ken
"pSm" <pSm@discussions.microsoft.com> wrote in message
news:7DF86AC8-663D-4AAE-8A45-68A2BF8DE4B6@microsoft.com...
> Ken,
> Here's the server 'Type' -->
> --------------------------------------------------------------------------
------------------
> Imports System.Diagnostics
> Public Class clsRemoteType
> Inherits MarshalByRefObject
>
> Private arrIDs(10) As String
> Private Shared lastid As String
>
> Private Shared message As String
> Private count As Integer = 0
> Public evt As New System.Diagnostics.EventLog("RemoteLog.txt")
>
> Public Sub clsRemoteType()
>
> evt.WriteEntry("APP", "Remote Type Created")
> End Sub
>
> Protected Overrides Sub finalize()
> evt.WriteEntry("APP", "Remote Type Destroyed" +
CStr(DateTime.Now))
> End Sub
>
> Public Sub send(ByVal id As String, ByVal msg As String)
> Dim i As Integer
> Dim blnFound As Boolean
> For i = 0 To count
> If (arrIDs(i) = id) Then
> 'Found - Already present no need to add
> blnFound = True
> Exit For
> End If
> Next
>
> If (Not blnFound) Then
> arrIDs(count) = id
> count = count + 1
> End If
> lastid = id
> message = msg
>
> evt.WriteEntry("APP", "Message written -" + message +
> CStr(DateTime.Now))
> End Sub
>
> Public Function receive() As String
> Return (lastid + " : " + message)
> End Function
> End Class
> --------------------------------------------------------------------------
------------------
> The Host -->
>
> Imports System
> Imports System.Runtime.Remoting
> Module Module1
>
> Sub Main()
> Try
> RemotingConfiguration.Configure("../RemotingHost.exe.config")
> Console.Write("Waiting for Connections to arrive --")
>
> Console.ReadLine()
>
> Catch ex As Exception
> Console.Write("Exception Occured..")
> End Try
> End Sub
>
> End Module
>
> --------------------------------------------------------------------------
-----------------
>
> The Server 'Config'
>
> <?xml version="1.0" encoding="utf-8" ?>
> <configuration>
> <system.runtime.remoting>
> <application>
> <service>
> <wellknown
> mode="Singleton"
> type="clsRemoteType, RemoteType.clsRemoteType"
> objectUri="RemoteTypeURI.rem"
> />
> </service>
> <channels>
> <channel ref="http" port="8989"/>
> </channels>
> </application>
> </system.runtime.remoting>
> </configuration>
>
> --------------------------------------------------------------------------
--------------------
> The client -->
>
> Code when a message is sent :
>
> Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnSend.Click
> Dim obj As New RemoteType.clsRemoteType
> obj.send("ABC", txtMsg.Text)
> End Sub
>
> Code that polls ( a timer is used)
>
> Private Sub tmPollMsg_Tick(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles tmPollMsg.Tick
> Dim obj As New RemoteType.clsRemoteType
> Dim str As String
> str = obj.receive()
> If Trim(str) <> ":" And lastmessage <> str Then
> lblMsg.Text = lblMsg.Text + str + vbCrLf
> lastmessage = str
> End If
> End Sub
> --------------------------------------------------------------------------
----------------
> Client Config -->
> <?xml version="1.0" encoding="utf-8" ?>
> <configuration>
> <system.runtime.remoting>
> <application>
> <client>
> <wellknown
> type="clsRemoteType, RemoteType.clsRemoteType"
> url="http://FLL020361:8989/RemoteTypeURI.rem"
> />
> </client>
> </application>
> </system.runtime.remoting>
> </configuration>
>
> ---------------------------***************--------------------------------
-----
>
> Thanks
>
>
> "Ken Kolda" wrote:
>
> > If the class is exposed as a singleton, the Message value should be
shared
> > across all clients. The fact that you're seeing the object destroyed
after
> > each call from a client implies this is SingleCall instead of Singleton
> > (although even then I wouldn't expect the finalizer to run right away
unless
> > your forcing garbage collection). You want to post some code if you
still
> > have issues.
> >
> > Ken
> >
> >
> > "pSm" <pSm@discussions.microsoft.com> wrote in message
> > news:B31F2E03-2A5C-4E32-B9EC-FC7EB29E84D4@microsoft.com...
> > > Hi Sam,
> > > Thanks for the post , but I am not really looking on how to
> > implement
> > > the chat program, but understanding/clearing my remoting concepts.
> > >
> > > To re-iterate, I would like to know if my understanding that if the
object
> > > is singleton, and the message property is shared, every user would
have
> > > access to the same message value, is correct or not ?
> > >
> > > Thanks,
> > >
> > >
> > > "Sam Santiago" wrote:
> > >
> > > > Here's a remoting Chat example that uses events to accomplish what
you
> > want.
> > > > Also, if you are seeing the finalizer run each time you might have
> > defined a
> > > > SingleCall SAO vs. a Singleton SAO. Check out this example for more
> > info:
> > > >
> > > > http://support.microsoft.com/default.aspx?scid=kb;en-us;312114
> > > >
> > > > Thanks,
> > > >
> > > > Sam
> > > >
> > > > --
> > > > _______________________________
> > > > Sam Santiago
> > > > ssantiago@n0spam-SoftiTechture.com
> > > > http://www.SoftiTechture.com
> > > > _______________________________
> > > > "pSm" <pSm@discussions.microsoft.com> wrote in message
> > > > news:1DD1BB89-DC6E-422A-A8E7-C0BB2F05A273@microsoft.com...
> > > > > Hi,
> > > > > I was trying to write a basic chat client/server. I used remoting
for
> > > > this.
> > > > > The server type uses a shared property message to keep track of
the
> > last
> > > > sent
> > > > > message. All the clients poll the server every 10ms to see if a
new
> > > > message
> > > > > is arrived.
> > > > >
> > > > > The server type is singleton. My guess was since the object is
> > singleton
> > > > and
> > > > > message is shared, the last mesage posted by anyone would be
visible
> > to
> > > > > anybody else.
> > > > >
> > > > > For example, say A says 'Hi' . When B polls for the message, he
should
> > see
> > > > > the 'Hi'. But what I see is, every client is seeing only the
message
> > that
> > > > he
> > > > > has posted and nothing else. So, if A says 'Hi' and B says 'Bye',
A
> > only
> > > > sees
> > > > > 'Hi' and B only sees 'Bye'. Can anyone help me understand what's
wrong
> > ?
> > > > >
> > > > > Second question is, after I saw that this was happening, I tried
> > finding
> > > > out
> > > > > if the object is getting destroyed. So I put in a finalizer and
some
> > logs
> > > > in
> > > > > it. I see the finalizer run after every call from the client.Why
is
> > this
> > > > so ?
> > > >
> > > >
> > > >
> >
> >
> >
- Next message: Petr Votocek: "format of binary serialized data..."
- Previous message: Ken Kolda: "Re: Singleton Objects"
- In reply to: pSm: "Re: Singleton Objects"
- Next in thread: pSm: "Re: Singleton Objects"
- Reply: pSm: "Re: Singleton Objects"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
