RE: Need help using tcpClient and tcpListner
From: hamil (hamil_at_discussions.microsoft.com)
Date: 10/14/04
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Date: Wed, 13 Oct 2004 21:11:02 -0700
I am withdrawing this question.
As I have read, even the connect property of the socket doesn't give current
status.
"hamil" wrote:
> I am having trouble using the TcpListener and TcpClient classes.
>
> At the end of this post is server code that runs, and a class whose purpose
> is described below.
>
> I need to know when the client closes the connection so I can exit my
> listener code. Here is what I have tried.
>
> First I asked MSDN and they said..
>
> TcpClient creates a Socket to send and receive data over a network. Classes
> deriving from TcpClient can use this property to get or set this Socket. Use
> the underlying Socket returned from Client if you require access beyond that
> which TcpClient provides. You can also use Client to set the underlying
> Socket to an existing Socket. This might be useful if you want to take
> advantage of the simplicity of TcpClient using a pre-existing Socket.
>
> So, I created a class called MyTcpClient, below, that inherited from
> TcpClient. I got this code from the MSDN library. Then I changed all
> occurances of TcpClient to MyTcpClient in my code. By doing this, I thought I
> could then query the property 'IsConnected'.
>
> The idea here is to be able to get at the 'protected connected' property of
> the underlying socket.
>
> However, when I try this, the line of code.
>
> tcpCli = tcpList.AcceptTcpClient()
>
> gives this error during the pre compile phase.
>
>
> C:\Documents and Settings\hcooper.JOE\My Documents\Visual Studio
> Projects\SystemNetDemo\TCPListenerForm.vb(140): Option Strict On disallows
> implicit conversions from 'System.Net.Sockets.TcpClient' to
> 'SystemNetDemo.MyTcpClient'.
>
>
> so I then insert option strict off at the top of my class. The precompiled
> error goes away but when it runs, I get the following error.
>
>
> An unhandled exception of type 'System.InvalidCastException' occured in
> SystemNetDemo.exe
> Additional information: Specified cast is not valid.
>
>
> Any help here???
>
> Hamil.
>
>
>
>
>
> ************************ MyTcpClient class
>
> Imports System.Net.Sockets
>
> Public Class MyTcpClient
>
> Inherits TcpClient
>
> Public IsConnected As Boolean
>
> Public Sub New()
> End Sub 'New
>
> Public Sub UsingProtectedMethods()
>
> 'Uses the protected 'Active' property belonging to the TcpClient
> base class
> 'to determine if a connection is established.
> If Me.Active Then
> ' Calls the protected 'Client' property belonging to the
> TcpClient base class.
> Dim s As Socket = Me.Client
> 'Uses the Socket returned by Client to set an option that is not
> available using TcpClient.
> IsConnected = s.Connected
> End If
> 'To free all resources, calls protected virtual method Dispose
> belonging to the TcpClient base class.
> Me.Dispose(True)
> GC.SuppressFinalize(Me)
> End Sub 'UsingProtectedMethods
>
> End Class
>
>
>
> ************ This code runs ........
>
> Imports System.IO
> Imports System.net
> Imports System.Net.Sockets
> Imports System.Threading
>
> Public Class TCPListenerForm
> Inherits System.Windows.Forms.Form
>
> Dim listening As Boolean
> Dim localhostAddress As IPAddress
> Dim port As Integer
> Dim tcpList As TcpListener
> Dim tcpCli As TcpClient
> Dim ns As NetworkStream
> Dim sr As StreamReader
> Dim receivedData As String
> Dim returnedData As String
> Dim sw As StreamWriter
>
> Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnStart.Click
> btnStart.Enabled = False
> btnStop.Enabled = True
> Dim tr As New Thread(AddressOf ListenToClients)
> tr.Start()
> End Sub
>
> Sub ListenToClients()
> localhostAddress = IPAddress.Loopback
> port = CInt(txtPort.Text)
> tcpList = New TcpListener(localhostAddress, port)
> tcpList.Start()
> listening = True
> Do While listening
> Do While tcpList.Pending = False And listening = True
> Thread.Sleep(10)
> Loop
> If Not listening Then Exit Do
> Dim tcpCli As New TcpClient
> tcpCli = tcpList.AcceptTcpClient()
> ns = tcpCli.GetStream
> sr = New StreamReader(ns)
> sw = New StreamWriter(ns)
> tbStatus.Text = "connected"
> Do While listening = True
> Thread.Sleep(10)
> receivedData = sr.ReadLine
> If receivedData <> Nothing Then
> returnedData = receivedData.ToUpper
> sw.WriteLine(returnedData)
> sw.Flush()
> End If
> Loop
> sr.Close()
> sw.Close()
> ns.Close()
> tcpCli.Close()
> tbStatus.Text = "closed"
> Loop
> tcpList.Stop()
> End Sub
>
> Private Sub btnStop_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnStop.Click
> btnStart.Enabled = True
> btnStop.Enabled = False
> listening = False
> End Sub
> End Class
>
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- In reply to: hamil: "Need help using tcpClient and tcpListner"
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