Udpclient sometimes throws exception - vb.net

Question

I'm currently working on a UDP communication PC <-> ARM LM3S6965 (Luminary) through the Ethernet. On the PC there is a VB.net application that simulates a UDP server/client.
the message is broadcasted from Vb.net application to ARM LM3S6965 based device, and in return response is sent from ARM Device to vb.net application.
but sometimes receive UdpClient throws socket exception i.e. Only one usage of each socket address (protocol/network address/port) is normally permitted.
the line which throws exception is
udpReceivingClient = New UdpClient(mnPort)
Complete VB.net Code is as follows
Module mod_Search_UDP
Public mnPort As Int32 = 3040 'Port number to send/recieve data on
'Public Const msBroadcastAddress As String = "255.255.255.255" 'Sends data to all LOCAL listening clients, to send data over WAN you'll need to enter a public (external) IP address of the other client
'Dim endPoint As IPEndPoint = New IPEndPoint(msBroadcastAddress, mnPort)
Public udpReceivingClient As UdpClient 'Client for handling incoming data
Public udpSendingClient As UdpClient 'Client for sending data
Public receivingThread As Thread 'Create a separate thread to listen for incoming data, helps to prevent the form from freezing up
Public mbiClosing As Boolean = False 'Used to close clients if form is closing
Public mbiCloseRxClient As Boolean = False
Public Sub InitializeSender()
Dim soc As Socket
Dim lsPort As String
Dim lnPort As Int32 = 3040
Const lsBroadcastAdd As String = "255.255.255.255"
'Dim endPoint As IPEndPoint = New IPEndPoint(msBroadcastAddress, mnPort)
'udpSendingClient = New UdpClient(endPoint)
udpSendingClient = New UdpClient(lsBroadcastAdd, lnPort)
udpSendingClient.EnableBroadcast = True
soc = udpSendingClient.Client
lsPort = (CType(soc.LocalEndPoint, IPEndPoint).Port.ToString())
mnPort = Convert.ToInt32(lsPort)
End Sub
Public Sub InitializeReceiver()
'Create UdpClient class and bind it to the local port number provided
'Try
udpReceivingClient = New UdpClient(mnPort)
'udpReceivingClient.EnableBroadcast = True
mbiCloseRxClient = True
'Catch ex As Exception
' MsgBox(ex.ToString)
'End Try
Dim start As ThreadStart = New ThreadStart(AddressOf MT_Receiver)
receivingThread = New Thread(start)
receivingThread.IsBackground = True
receivingThread.Start()
End Sub
Public Sub MT_Receiver()
Dim endPoint As IPEndPoint = New IPEndPoint(IPAddress.Any, mnPort) 'Listen for incoming data from any IP address on the specified port
Dim lbData() As Byte 'Buffer for storing incoming bytes
Dim llRet As UInt16
'udpListen.Poll(1000, Net.Sockets.SelectMode.SelectRead)
While (True) 'Setup an infinite loop
If mbiClosing = True Then 'Exit sub if form is closing
Exit Sub
End If
llRet = udpReceivingClient.Available
If llRet > 0 Then
lbData = udpReceivingClient.Receive(endPoint) 'Receive incoming bytes
'If udpListen.Available Then
' udpListen.Receive(lbData, 256, Net.Sockets.SocketFlags.None)
'End If
'If lbData Is Nothing Then
'Else
frmSearchUDP.MT_Validate_Msg(lbData)
End If
End While
End Sub
Public Sub MT_Send_UDP(ByVal lbTxBuffer() As Byte)
InitializeSender()
If mbiCloseRxClient = True Then
receivingThread.Abort()
udpReceivingClient.Client.Dispose()
udpReceivingClient.Close()
End If
Try
udpSendingClient.Send(lbTxBuffer, lbTxBuffer.Length)
Catch ex As Exception
MsgBox(ex.ToString)
End Try
udpSendingClient.Client.Dispose()
udpSendingClient.Close()
InitializeReceiver()
'Try
' udpReceivingClient.BeginReceive(AddressOf MT_RX_Callback, Nothing)
'Catch ex As Exception
' MsgBox(ex.ToString)
'End Try
End Sub
End Module
Whats mistake is there in code ? how can i use same port for receive and transmit ?