UDP SocketException - Only one usage of each socket address is normally permitted - vb.net

Question

As much as there are many questions on here that are very similar, none of the supplied answers have helped me, which makes me sad :(
I've got a very large management system that I've been tasked to write some UDP packet sending/receiving for. I'd already written a prototype and all was well, so I started merging my code into said system. However, I've now got a (not show-stopping, but annoying) SocketException popping up:
System.Net.Sockets.SocketException occurred
ErrorCode=10048
Message=Only one usage of each socket address (protocol/network address/port) is normally permitted
NativeErrorCode=10048
Source=System
StackTrace:
at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Bind(EndPoint localEP)
at System.Net.Sockets.UdpClient..ctor(Int32 port, AddressFamily family)
at System.Net.Sockets.UdpClient..ctor(Int32 port)
at Goose.Job.DeviceServerUDPReceiver.InitialiseReceiverClient() in C:\WORK\Trunk\GooseOrders\Classes\SheetCounter\DeviceServerUDPReceiver.vb:line 39
Here is the UDPReceiver class - Which is responsible for just sitting in a loop and waiting for responses from the Device Servers we've got dotted about the place.
Public Class DeviceServerUDPReceiver : Implements IDisposable
'///////////////////////////////////////////////////////////////////////////////
' CONSTANTS
'///////////////////////////////////////////////////////////////////////////////
Private Const TIBBO_DEVICE_REPLY_CMD_START As Integer = 0
Private Const TIBBO_DEVICE_REPLY_CMD_END As Integer = 3
Private Const TIBBO_MESSAGE_REPLY_DIVIDER As String = "_"
Private Const TIBBO_DEVICE_REPLY_OK As String = "OK"
'///////////////////////////////////////////////////////////////////////////////
' MEMBER VARIABLES
'///////////////////////////////////////////////////////////////////////////////
Public _ReceivingClient As System.Net.Sockets.UdpClient
Public _iReceivingPort As Integer = 2002
Public _thReceivingThread As System.Threading.Thread
Public _bClosing As Boolean
'///////////////////////////////////////////////////////////////////////////////
' EVENTS
'///////////////////////////////////////////////////////////////////////////////
Public Event GotDeviceResponse(ByVal sResponse As String)
Public Event FoundNewDevice(ByVal TibboObject As TibboDevice)
'///////////////////////////////////////////////////////////////////////////////
' METHODS
'///////////////////////////////////////////////////////////////////////////////
' Initialises the UDP receiver client on the specified port number. Then runs
' a listening thread constantly waiting to receive udp messages
Public Sub InitialiseReceiverClient()
Try
' TODO - FIX SOCKET EXCEPTION HERE - NOT THREAD ISSUE - THIS IS DUE TO
' THE SOCKET NOT BEING CLOSED. BUT SEEING HOW UDP IS CONNECTIONLESS .... ?!
_ReceivingClient = New System.Net.Sockets.UdpClient(_iReceivingPort)
Dim thStartThread As Threading.ThreadStart = New Threading.ThreadStart(AddressOf SitAndReceive)
_thReceivingThread = New Threading.Thread(thStartThread)
_thReceivingThread.IsBackground = True
_thReceivingThread.Start()
Catch ex As System.Net.Sockets.SocketException
Console.WriteLine("Socket Exception: " & ex.Message)
Finally
End Try
End Sub
' The endless loop listener thread. Will sit and wait for udp packets to
' process
Private Sub SitAndReceive()
Dim epEndPoint As System.Net.IPEndPoint = New System.Net.IPEndPoint(System.Net.IPAddress.Any, _iReceivingPort)
' infinite loop to listen for udp messages
While (_bClosing = False)
Try
Dim sMessage As String = ""
Dim byData() As Byte
byData = _ReceivingClient.Receive(epEndPoint)
sMessage = System.Text.Encoding.ASCII.GetString(byData)
Console.WriteLine(sMessage)
ProcessIncomingUDPDataMessage(sMessage)
Catch ex As System.Net.Sockets.SocketException
Console.WriteLine(ex.Message)
End Try
End While
End Sub
' close the connection to the receiving udp socket
Public Sub Close()
_bClosing = True
End Sub
' Processes incoming udp packets for answeres from the device servers
Private Sub ProcessIncomingUDPDataMessage(ByVal sMessage As String)
' UDP Data packet from Tibbo devices is set out as follows
'
' CMD_ANSWER
' Where "CMD" = The command the device is replying too and
' "ANSWER" = It's reply
Select Case sMessage.Substring(TIBBO_DEVICE_REPLY_CMD_START, TIBBO_DEVICE_REPLY_CMD_END)
Case TibboDevice.DEVICE_COMMAND_ATO
'/////////////////////////////////////////////////////////////////////////
' Any Tibbo's out there reply message
'/////////////////////////////////////////////////////////////////////////
Dim s() As String = sMessage.Split(TIBBO_MESSAGE_REPLY_DIVIDER)
Dim sMacAddress As String = s(2) ' the replying devices' mac address
Dim sIpAddress As System.Net.IPAddress = System.Net.IPAddress.Parse(s(3)) ' ip
Dim sNetBiosName As String = s(1) ' netbios name
Dim iTibboStatus As TibboDevice.ETIIBO_DEVICE_STATE = TibboDevice.ETIIBO_DEVICE_STATE.TIBBO_DEVICE_STATE_BAD ' status
' set this device status depending on the reply
If s(4) = TIBBO_DEVICE_REPLY_OK Then
iTibboStatus = TibboDevice.ETIIBO_DEVICE_STATE.TIBBO_DEVICE_STATE_OK
End If
' create a new tibbo device to pass back to the main form
Dim Tibbo As TibboDevice = New TibboDevice(sMacAddress, sIpAddress, sNetBiosName, iTibboStatus)
' raise event to add this to our list
RaiseEvent FoundNewDevice(Tibbo)
Case TibboDevice.DEVICE_COMMAND_STS
'//////////////////////////////////////////////////////////////////////////
' Status reply message
'//////////////////////////////////////////////////////////////////////////
Dim s() As String = sMessage.Split(TIBBO_MESSAGE_REPLY_DIVIDER)
Dim sResult As String = ""
' format our string nicely
sResult &= "Mac Address: " & vbTab & vbTab & s(1)
sResult &= Environment.NewLine & "IP Address: " & vbTab & vbTab & s(2)
sResult &= Environment.NewLine & "Device Name: " & vbTab & vbTab & s(3)
sResult &= Environment.NewLine & "TiOS FW: " & vbTab & vbTab & s(4)
sResult &= Environment.NewLine & "Goose SC FW: " & vbTab & vbTab & s(5)
sResult &= Environment.NewLine & "System Uptime: " & vbTab & vbTab & s(6)
sResult &= Environment.NewLine & "System Time: " & vbTab & vbTab & s(7)
sResult &= Environment.NewLine & "System Status: " & vbTab & vbTab & s(8)
RaiseEvent GotDeviceResponse(sResult)
Case TibboDevice.DEVICE_COMMAND_ASC
'////////////////////////////////////////////////////////////////////////////
' Average sheet count message
'////////////////////////////////////////////////////////////////////////////
Dim s() As String = sMessage.Split(TIBBO_MESSAGE_REPLY_DIVIDER)
Dim sResult As String = ""
RaiseEvent GotDeviceResponse(sResult)
Case TibboDevice.DEVICE_COMMAND_NAM
'////////////////////////////////////////////////////////////////////////////
' Changed device name reply message
' Device will reply NAM_[NEWNAME] - once it's set it's new name
'////////////////////////////////////////////////////////////////////////////
Dim s() As String = sMessage.Split(TIBBO_MESSAGE_REPLY_DIVIDER)
Dim sResult As String = ""
RaiseEvent GotDeviceResponse(sResult)
Case TibboDevice.DEVICE_COMMAND_IDX
'////////////////////////////////////////////////////////////////////////////
' Device responds with it's device id
'////////////////////////////////////////////////////////////////////////////
Dim s() As String = sMessage.Split(TIBBO_MESSAGE_REPLY_DIVIDER)
Dim sResult As String = ""
' TODO - do something with the result
Case TibboDevice.DEVICE_COMMAND_RBT
'////////////////////////////////////////////////////////////////////////////
' Device is going down for a reboot - not much to do here, we have to wait
'////////////////////////////////////////////////////////////////////////////
Case TibboDevice.DEVICE_COMMAND_BUZ
'////////////////////////////////////////////////////////////////////////////
' Device has played it's buzz sound - ignore
'////////////////////////////////////////////////////////////////////////////
Case TibboDevice.DEVICE_COMMAND_FSH
'////////////////////////////////////////////////////////////////////////////
' Device flashed it's LEDs - ignore
'////////////////////////////////////////////////////////////////////////////
Case TibboDevice.DEVICE_COMMAND_AIP
'////////////////////////////////////////////////////////////////////////////
' Device replies with it's actual ip address
'////////////////////////////////////////////////////////////////////////////
Dim s() As String = sMessage.Split(TIBBO_MESSAGE_REPLY_DIVIDER)
Dim sResult As String = ""
' TODO - do something with the result
Case TibboDevice.DEVICE_COMMAND_CBC
'////////////////////////////////////////////////////////////////////////////
' Device replies with it's current box count
'////////////////////////////////////////////////////////////////////////////
Dim s() As String = sMessage.Split(TIBBO_MESSAGE_REPLY_DIVIDER)
Dim sResult As String = ""
' TODO - do something with the result
Case TibboDevice.DEVICE_COMMAND_STP
'////////////////////////////////////////////////////////////////////////////
' Device has been stopped - won't reply. Only way to bring it back to life
' is to press the 'reset' button on the actual unit - ignore
'////////////////////////////////////////////////////////////////////////////
End Select
End Sub
Protected Overridable Overloads Sub Dispose(disposing As Boolean)
If (disposing) Then
' free managed objects
'_ReceivingClient = Nothing
_bClosing = True
End If
End Sub
Public Overloads Sub Dispose() Implements IDisposable.Dispose
Dispose(True)
GC.SuppressFinalize(Me)
End Sub
End Class
Now, all I'm doing in the main form, is: When my listener form is closed - I want to close the listener down (obviously)... For this, I'm using Dispose(). However, when someone wants to start it up again, said exception occurs on the byData = _ReceivingClient.Receive(epEndPoint) line in the SitAndReceive procedure.
Since UDP is transaction based and its sockets (possibly theoretically) can't be in a CLOSE_WAIT state, what is stopping me from closing it down and then immediately relaunching the listener?
I must admit I'm new to UDP sockets, so far however, I've found them a joy to work with and even though this exception wouldn't crash an end-users software (with a simple try/catch), it does have me intrigued and I'd like to understand why it's happening.
Any help is very much appreciated.

Answer 1

Managed to figure this out in the end. Apparently if you want to have more than one connection to a socket, you have to manually configure it, like so:
Dim endPoint = New System.Net.IPEndPoint(0, _iReceivingPort)
_ReceivingClient = New System.Net.Sockets.UdpClient()
_ReceivingClient.ExclusiveAddressUse = False
_ReceivingClient.Client.SetSocketOption(Net.Sockets.SocketOptionLevel.Socket, Net.Sockets.SocketOptionName.ReuseAddress, True)
_ReceivingClient.Client.Bind(endPoint)
Works now, so I'm happy.