VB TCP Chat geht nicht

Imports System.Net.Sockets, System.Threading, System.IO

Public Class Form1

    Dim Listener As New TcpListener(7000)
    Dim Client As TcpClient
    Dim Message As String


    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles Me.FormClosing
        Listener.Stop()
        Application.Exit()
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
        Listener.Start()
        Dim listthread As New Thread(New ThreadStart(AddressOf listening))
        listthread.Start()
    End Sub
    Private Sub listening()
        Listener.Start()
    End Sub

    Private Sub btnSendMsg_Click(sender As Object, e As EventArgs) Handles btnSendMsg.Click
        If rtbTextToSend.Text = "" Thensn
            MsgBox("Geben Sie bitte einen Text ein!", MsgBoxStyle.Exclamation, "Kein Text!")
        Else
            Try
                Client = New TcpClient(tbip.Text, 7000)
                Dim writer As New StreamWriter(Client.GetStream())
                writer.Write(rtbTextToSend.Text)
                rtbReceeivedText.AppendText(Format(Now, "[dd.MM | hh:mm:ss]]") & " Du: " & rtbTextToSend.Text & vbCrLf)
                rtbTextToSend.Clear()
                writer.Flush()
            Catch ex As Exception
                MsgBox("Fehler", MsgBoxStyle.Exclamation)
            End Try
        End If
    End Sub

    Private Sub tmrlistener_Tick(sender As Object, e As EventArgs) Handles tmrlistener.Tick
        If Listener.Pending = True Then
            Message = ""
            Client = Listener.AcceptTcpClient()

            Dim Reader As New StreamReader(Client.GetStream())
            While Reader.Peek > -1
                Message = Message + Convert.ToChar(Reader.Read()).ToString

            End While
            rtbReceeivedText.AppendText(Format(Now, "[dd.MM | hh:mm:ss]]") & " Er/Sie " & Message & vbCrLf)
        End If
    End Sub
End Class