Named pipe server remains "waiting for connection" after close and aborting its thread

I create a thread which creates three new threads with a named pipe server in each thread.

                serverThread = New Thread(AddressOf enableClientRequests)
                serverThread.Start()
....
 Friend Sub enableClientRequests()
        Dim i As Integer
        For i = 0 To OptMaxConcurrentClients - 1
            managerIFlist(i) = New clsPhotExManagerInterface
            servers(i) = New Thread(AddressOf managerIFlist(i).server)
            servers(i).Start()
        Next i
        Thread.Sleep(250)
        While i > 0
            For j As Integer = 0 To OptMaxConcurrentClients - 1
                If Not (servers(j) Is Nothing) Then
                    If servers(j).Join(250) Then
                        servers(j) = Nothing
                        i -= 1    ' decrement the thread watch count
                    End If
                End If
            Next j
        End While
    End Sub
...
Public Class clsPhotExManagerInterface

#Region "PhotExPackage requests"
    Private pipeServer As NamedPipeServerStream

    Public Sub server()
        pipeServer = New NamedPipeServerStream("PhotExPipe", PipeDirection.InOut, OptMaxConcurrentClients)
        Do
            pipeServer.WaitForConnection()
           ... do work
            pipeServer.Disconnect()
        Loop
    End Sub
    Public Sub serverClose()
        pipeServer.Close()
    End Sub

When I want to stop accepting request, and in the Application.close event, I close them all down....

 Private Sub closePackageServer()
        If serverThread IsNot Nothing Then
            For j As Integer = 0 To OptMaxConcurrentClients - 1
                managerIFlist(j).serverClose()
                If servers(j) IsNot Nothing Then
                    servers(j).Abort()
                    servers(j) = Nothing
                    managerIFlist(j) = Nothing
                End If
            Next j
            serverThread.Abort()
        End If
    End Sub

This invokes the serverClose method on all three threads but the application does not close. Clicking Pause in Visual Studio

shows the code ay the pipeServer.WaitForConnection statement.

How can I close it?