Sockets (connecting and closing)

I am using VB .Net to explore Sockets for the first time. My task is simple: create a socket, connect to a web server, download the stream, display it in a rich textbox, disconnect, connect to another server.

My problem: I can't do the last part of the tast 'connect to another server.'

When I try to reconnect, I get the following error:

System.ObjectDisposedException: Cannot access a disposed object named "System.Net.Sockets.Socket".
Object name: "system.Net.Sockets.Socket".
at System.Sockets.Socket.Connect(EndPoint remoteEP)
at LearningVBData.sockclient.btnConnect_Click(Object sender, EventArgs e) in [source location]
line 122

How can I close a Socket, and reconnect to a new or the same location using the same Socket?

VB Code:

'Global declarations 
    Dim strRetPage As String = Nothing 
    Dim server As String = Nothing 
 
    'Creates the Socket for sending data over TCP. 
    Dim sock As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) 
 
 
    Private Sub btnConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConnect.Click 
        server = txtServer.Text 
        Dim hostadd As System.Net.IPAddress = System.Net.Dns.Resolve(server).AddressList(0) 
        Dim EPhost As New System.Net.IPEndPoint(hostadd, 80) 
 
        Try 
            sock.Connect(EPhost) 
        Catch ex As Exception 
            MsgBox("Socket error: " & ex.ToString(), vbExclamation) 
        End Try 
 
        If Not sock.Connected Then 
            MsgBox("Socket error: " _ 
                & Convert.ToString(System.Runtime.InteropServices.Marshal.GetLastWin32Error()), vbExclamation) 
        Else 
            Me.Text = "Sockclient - Connected" 
        End If 
 
    End Sub 
 
    Private Sub btnDisconnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisconnect.Click 
        Try 
            sock.Shutdown(SocketShutdown.Both) 
        Catch ex As Exception 
            MsgBox("Socket error: " & ex.ToString(), vbExclamation) 
        End Try 
 
        sock.Close() 
 
        If sock.Connected Then 
            MsgBox("Socket error: " _ 
                & Convert.ToString(System.Runtime.InteropServices.Marshal.GetLastWin32Error()), vbExclamation) 
        Else 
            Me.Text = "Sockclient - Disconnected" 
        End If 
    End Sub 
 
    Private Sub btnPopulate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPopulate.Click 
        Dim ASCII As System.Text.Encoding = System.Text.Encoding.ASCII 
        Dim StrGet As String = "GET / HTTP/1.1" & ControlChars.CrLf & _ 
                            "Host: " & server & ControlChars.CrLf & _ 
                            "Connection: Close" & ControlChars.CrLf & _ 
                            ControlChars.CrLf 
        Dim ByteGet As Byte() = ASCII.GetBytes(StrGet) 
        Dim RecvBytes(256) As Byte 
 
        Try 
            ' Sends the GET text to the host 
            sock.Send(ByteGet, ByteGet.Length, 0) 
        Catch ex As Exception 
            MsgBox("Socket error: " & ex.ToString(), vbExclamation) 
            Return 
        End Try 
 
        ' Receives the page, looping until all bytes are received 
        Dim bytes As Int32 = sock.Receive(RecvBytes, RecvBytes.Length, 0) 
        strRetPage = "Default HTML page on " & server & ":" & ControlChars.CrLf 
        strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0, bytes) 
 
        While bytes > 0 
            bytes = sock.Receive(RecvBytes, RecvBytes.Length, 0) 
            strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0, bytes) 
        End While 
 
        txtData.Text = strRetPage 
 
    End Sub