Is Client Still Connected To The Server

[darkzidedemigod]

Hi everyone! My first post here in vb forums. I'm new to sockets programming since I migrated from Winsock and I learn a lot from Atheist. using his code, I can't access the messageReceived() every time a client sends a message on the server. but then I put a code to catch the message on sub doRead() and I can retrieve the message. My problem now is how can I determine if a client is still connected to the server or not so I can delete it on the ConnectedClient ?
ConnectedClient Class:

Public Class ConnectedClient
    Private mClient As System.Net.Sockets.TcpClient

    Private mUsername As String
    Private mParentForm As FrmServer
    Private readThread As System.Threading.Thread
    Private Const MESSAGE_DELIMITER As Char = ControlChars.Cr

    Public Event dataReceived(ByVal sender As ConnectedClient, ByVal message As String)

    Sub New(ByVal client As System.Net.Sockets.TcpClient, ByVal parentForm As FrmServer)
        mParentForm = parentForm
        mClient = client

        readThread = New System.Threading.Thread(AddressOf doRead)
        readThread.IsBackground = True
        readThread.Start()
    End Sub

    Public Property Username() As String
        Get
            Return mUsername
        End Get
        Set(ByVal value As String)
            mUsername = value
            mParentForm.SetConnectionLabelText(value)
        End Set
    End Property

    Private Sub doRead()
        Const BYTES_TO_READ As Integer = 255
        Dim readBuffer(BYTES_TO_READ) As Byte
        Dim bytesRead As Integer
        Dim sBuilder As New System.Text.StringBuilder

        
        Do
            If mClient.GetStream.DataAvailable Then
                bytesRead = mClient.GetStream.Read(readBuffer, 0, BYTES_TO_READ)

                If (bytesRead > 0) Then
                    Dim message As String = System.Text.Encoding.UTF8.GetString(readBuffer, 0, bytesRead)

                    mParentForm.SetConnectionLabelText(message) '<----message catcher

                    If (message.IndexOf(MESSAGE_DELIMITER) > -1) Then

                        Dim subMessages() As String = message.Split(MESSAGE_DELIMITER)

                        sBuilder.Append(subMessages(0))
                        RaiseEvent dataReceived(Me, sBuilder.ToString)
                        sBuilder = New System.Text.StringBuilder

                        If subMessages.Length = 2 Then
                            sBuilder.Append(subMessages(1))
                        Else
                            For i As Integer = 1 To subMessages.GetUpperBound(0) - 1
                                RaiseEvent dataReceived(Me, subMessages(i))
                            Next
                            sBuilder.Append(subMessages(subMessages.GetUpperBound(0)))
                        End If
                    Else
                        sBuilder.Append(message)
                    End If
                End If

            End If
        Loop

    End Sub

    Public Sub SendMessage(ByVal msg As String)
        Dim sw As IO.StreamWriter
        Try
            SyncLock mClient.GetStream
                sw = New IO.StreamWriter(mClient.GetStream)
                sw.Write(msg)
                sw.Flush()
            End SyncLock
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try

    End Sub
End Class

Server Side:

Imports System.Net, System.Net.Sockets, System.IO
Public Class FrmServer
    Private listener As System.Net.Sockets.TcpListener
    Private listenThread As System.Threading.Thread
    Private clients As New List(Of ConnectedClient)

    Private Sub doListen()
        Dim incomingClient As System.Net.Sockets.TcpClient
        Do
            incomingClient = listener.AcceptTcpClient
            Dim connClient As New ConnectedClient(incomingClient, Me)
            AddHandler connClient.dataReceived, AddressOf Me.messageReceived
            clients.Add(connClient)
        Loop
    End Sub

    Public Sub removeClient(ByVal client As ConnectedClient)
        If clients.Contains(client) Then
            clients.Remove(client)
        End If
    End Sub

    Private Sub messageReceived(ByVal sender As ConnectedClient, ByVal message As String)
        MsgBox(message)
        Dim data() As String = message.Split("|"c)
        Select Case data(0)
            Case "CONNECT"
                If GetClientByName(data(1)) Is Nothing Then
                    sender.SendMessage("You are Connected")
                    sender.Username = data(1)
                End If
            Case "DISCONNECT"
                removeClient(sender)
        End Select

    End Sub


    Private Function GetClientByName(ByVal name As String) As ConnectedClient
        For Each cc As ConnectedClient In clients
            If cc.Username = name Then
                Return cc 'client found, return it.
            End If
        Next
        'If we've reached this part of the method, there is no client by that name
        Return Nothing
    End Function
 
    Private Sub FrmServer_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        listener = New System.Net.Sockets.TcpListener(System.Net.IPAddress.Any, 43001) 'The TcpListener will listen for incoming connections at port 43001
        listener.Start() 'Start listening.
        listenThread = New System.Threading.Thread(AddressOf doListen) 'This thread will run the doListen method
        listenThread.IsBackground = True 'Since we dont want this thread to keep on running after the application closes, we set isBackground to true.
        listenThread.Start()
    End Sub

    Private Sub Btn_Send_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Btn_Send.Click

        lstlog.Items.Add(txtName.Text & " says " & txtMessage.Text)
        For Each cc As ConnectedClient In clients
            cc.SendMessage(txtName.Text & " says " & txtMessage.Text)
        Next

    End Sub

    Private Delegate Sub StringDelegate(ByVal text As String)

    Sub SetConnectionLabelText(ByVal text As String)
        If lstlog.InvokeRequired Then
            Me.Invoke(New StringDelegate(AddressOf SetConnectionLabelText), text)
        Else

            Dim Data() As String = text.Split("|"c)

            Select Case Data(0)
                Case "CONNECT"
                    lstlog.Items.Add(Data(1) & " is connected.")

                    For Each cc As ConnectedClient In clients
                        cc.SendMessage(Data(1) & " is connected.")
                    Next

                Case "MESSAGE"
                    lstlog.Items.Add(Data(1) & " says " & Data(2))

                    For Each cc As ConnectedClient In clients
                        cc.SendMessage(Data(1) & " says " & Data(2))
                    Next
            End Select
        End If
    End Sub

    Sub AddClientList(ByVal text As String)
        If lsvClients.InvokeRequired Then
            Me.Invoke(New StringDelegate(AddressOf AddClientList), text)
        Else

        End If
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        clients.Item(CInt(lsvClients.SelectedItems(0).Tag)).SendMessage(txtMessage.Text)
    End Sub
End Class

Note: the server runs on Win7 x64 ultimate and the clients are laptops on win7 x86. I read a comment that the server should be having a static IP address, but when did it together with the clients, It still doesn't work. I am just using a switch for the network.