Re: client close the socket. how the server knows?

From: rs (ahmed1979_at_gmail.com)
Date: 12/08/04 

Date: 8 Dec 2004 10:33:46 -0800

to clearify what i am doing. I building a chat program. many clients
connects to one server. I am using the async socket method. how would
the server know that the socket is closed from the client side.

Thanks
scorpion53061 wrote:
> Untested....
>
> Here is an example. Create a new windows app, add a checkbox a
listbox
> and
> a button. Start the app and check the checkbox to start the server
> (clear
> it to shut the server down). Once the server has started click the
> button
> to serialise/deseleralise the object through the socket. Obviously
this
> works standalone, but start two instances of the app and click the
> server
> checkbox on one and press the button on the other and you'll see the
> exact
> same code sending the object to a different app. This app could even
be
> on
> another machine.
>
> Imports System
> Imports System.IO
> Imports System.Runtime.Serialization
> Imports System.Xml.Serialization
> Imports System.Runtime.Serialization.Formatters.Binary
> Imports System.Net.Sockets
> Imports System.Net
>
> Public Class Form1
> Inherits System.Windows.Forms.Form
>
> Private Delegate Sub UpdateListBoxDel(ByVal Data As String)
> Private m_ListenerThread As Threading.Thread
> Private server As New TcpListener(IPAddress.Parse("127.0.0.1"), 5000)
>
> Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles Button1.Click
>
> ' Create a new object that is populated with data
> Dim obj As New MyObject(1, "Adrian", "Forbes")
> ' Create an XmlSerializer for the MyObject type
> Dim formatter As New XmlSerializer(GetType(MyObject))
>
> ' Create new TcpClient
> Dim client As TcpClient = New TcpClient
>
> ' Connect to port 5000 on the local machine
> UpdateDisplay("Connecting to client", True)
> client.Connect("127.0.0.1", 5000)
>
> ' Get the underlying stream
> Dim stream As Stream = client.GetStream
>
> ' Seralise out instance of MyObject over the TcpClient's stream
> using the XmlSerializer
> UpdateDisplay("Sending..." & obj.ToString, True)
> formatter.Serialize(stream, obj)
>
> ' Close the stream
> stream.Close()
>
> End Sub
>
> Private Sub StartServer()
>
> ' This function is going to run until the server closes
> ' so set up a var that lets us know we want to run
> Dim bRunning As Boolean = True
>
> ' Start the server
> UpdateDisplay("Server starting")
> server.Start()
>
> While bRunning
> Try
> ' This method will block until a connection is accepted
> UpdateDisplay("Server waiting for connection...")
> Dim client As TcpClient = server.AcceptTcpClient()
>
> ' Now we have a TcpClient with an underlying stream
> ' so we want to deserialise our object. This is
> ' pretty much the sending code in reverse.
> UpdateDisplay("Server connected")
> Dim Formatter As XmlSerializer = New
> XmlSerializer(GetType(MyObject))
>
> Dim obj As MyObject =
> CType(Formatter.Deserialize(client.GetStream), MyObject)
>
> UpdateDisplay("Received " & obj.ToString)
> Catch
> ' If we get an error such as the connection getting
> ' closed from under us then signal to stop running
> bRunning = False
> End Try
>
> End While
>
> ' Stop the server
> Debug.WriteLine("Server stopping")
> server.Stop()
>
> End Sub
>
> Private Sub UpdateDisplay(ByVal Data As String)
> ' Invoke a call to update the listbox
> ListBox1.Invoke(New UpdateListBoxDel(AddressOf UpdateListBox), New
> Object() {Data})
> End Sub
>
> Private Sub UpdateDisplay(ByVal Data As String, ByVal Direct As
Boolean)
> If Direct Then
> ' This method will update the listbox on this thread
> UpdateListBox(Data)
> Else
> ' Otherwise use this method that will use the listbox's thread
> to
> ' do the update
> UpdateDisplay(Data)
> End If
> End Sub
>
> Public Sub UpdateListBox(ByVal Data As String)
> ListBox1.Items.Add(Data)
> Application.DoEvents()
> End Sub
>
> Private Sub Form1_Closing(ByVal sender As Object, ByVal e As
> System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
>
> If Not m_ListenerThread Is Nothing Then
> ' If the TcpListener is listening then shut it down
> StopServer()
> End If
>
> End Sub
>
> Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object,
> ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
> If CheckBox1.Checked Then
> ' The server checkbox has been clicked so kick off a new thread
> ' and run our StartServer method on it
> UpdateDisplay("Starting server")
> m_ListenerThread = New Threading.Thread(AddressOf StartServer)
> m_ListenerThread.Start()
> UpdateDisplay("Started")
> Else
> ' The checkbox has been unchecked so shut the server down
> UpdateDisplay("Stopping server", True)
> StopServer()
> UpdateDisplay("Stopped", True)
> End If
> End Sub
>
> Private Sub StopServer()
>
> ' Stop the TcpListener
> server.Stop()
> ' and wait here for the thread to exit. The above call will cause
> an
> ' exception in the listener thread so lets just wait until it is all
> ' closed up
> m_ListenerThread.Join()
>
> End Sub
> End Class
>
> <Serializable()> _
> Public Class MyObject
> Public EmployeeID As Long
> Public Forename As String
> Public Surname As String
>
> Public Sub New(ByVal EmployeeID As Long, ByVal Forename As String,
ByVal
> Surname As String)
> Me.EmployeeID = EmployeeID
> Me.Forename = Forename
> Me.Surname = Surname
> End Sub
>
> Public Sub New()
> Me.EmployeeID = 0
> Me.Forename = ""
> Me.Surname = ""
> End Sub
>
> Public Overrides Function ToString() As String
> Return EmployeeID.ToString & ": " & Surname & ", " & Forename
> End Function
>
> End Class
>
> "rs" <aa@d.com> wrote in message news:aa@d.com:
> > how I the client tell the server that the socket is closed? or this
there
> > an
> > even that informs the server that the clients socket is close?
> >
> > Oh, I am using vb.net 2003
> >
> > Thanks