Bad file name or number error in VB.Net

I have a form with two objects. One is of type MessageStore and the other NetListener, these are custom classes. NetListener listens for incoming messages from the network (this works fine). The MessageStore class works with a disk file opened using FileOpen.

What I want to do is when a new message arrives, to store it in the MessageStore. My code works as follows.

1. When a message arrives, my NetListener object raises an event, which is handled by a Sub in the main form.

2. From this event handler, when I try MessageStore.AddMessage(Msg) I get a "Bad file name or number" error in the AddMessage sub in the MessageStore class. The file number is 1 (same as when the file was opened and read from - file was not closed) but I get this error.

Calling MessageStore.AddMessage outside this even handler works without any error.

Any ideas as to why this does not work?


VB.Net 2005 (.Net 2.0)

I have the following classes:

Public Class InstantMessage - Defines a message structure (not included)

Code:

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Public Class MessageStore  'stores InstantMessage objects


#Region "Message Store Public Methods"

' Constructor

Public Sub New(ByVal FilePath As String)

Open(FilePath)

End Sub



' Creates or Opens an existing Message Store at the given path

Public Sub Open(ByVal FilePath As String)

' Clear the Array List and other variables

_MsgList.Clear()

_MsgCount = 0

_DeletedMsgCount = 0

_LastMsgID = 0

' Open the message store

OpenFile(FilePath)

End Sub



' Adds an InstantMessage to the Message Store

Public Overridable Sub AddMessage(ByVal msg As InstantMessage)

' Increment the last message ID and set the ID for the message

_LastMsgID += 1

msg.MsgID = _LastMsgID

' Save the message to the disk file

AddToFile(msg)

' Add the message to the ArrayList after saving the file

' to obtain the position of the record and message in the file.

' Remove the message part of the record from the ArrayList

msg.Message = ""

_MsgList.Add(msg)

_MsgCount += 1

End Sub

#End Region



#Region "Message Store Private Methods"

' Opens a disk file to store and retrieve InstantMessages

Private Sub OpenFile(ByVal FilePath As String)

Dim I As Integer

' Get a free file number and open the file specified in FilePath

_FileNum = FreeFile()

FileOpen(_FileNum, FilePath, OpenMode.Binary)

' Check if the file is empty, otherwise get the number of messages

If LOF(_FileNum) <> 0 Then

FileGet(_FileNum, _MsgCount)

FileGet(_FileNum, _DeletedMsgCount)

Else

' Create a new file structure

FilePut(_FileNum, _MsgCount)

FilePut(_FileNum, _DeletedMsgCount)

End If

' Get details of all messages in the store and store them in

' the ArrayList _MsgList

For I = 1 To _MsgCount

Dim Message As New InstantMessage

GetMessageHeaderFromFile(Message)

_LastMsgID = Message.MsgID

' Do not allow the ArrayList to have deleted messages.

If Not Message.Deleted Then

_MsgList.Add(Message)

Else

' Distroy the message object

Message = Nothing

_DeletedMsgCount += 1

End If

Next

End Sub



' Adds an Instant Message to the Message Store on disk

Private Sub AddToFile(ByRef msg As InstantMessage)

'Dim TmpPos As Integer

' Goto the end of the file and add the new message

' Check if the file is empty

If LOF(_FileNum) > 0 Then

Seek(_FileNum, LOF(_FileNum) + 1)

End If

' Get the position of the record in the disk file

msg.RecordStartPos = Seek(_FileNum)

FilePut(_FileNum, msg.MsgID)

' Save the length of the HostName and then the HostName

FilePut(_FileNum, msg.HostName.Trim.Length)

FilePut(_FileNum, msg.HostName.Trim)

' Save the length of the UserName and then the UserName

FilePut(_FileNum, msg.UserName.Trim.Length)

FilePut(_FileNum, msg.UserName.Trim)

FilePut(_FileNum, msg.MsgDateTime)

FilePut(_FileNum, msg.Priority)

' Save the length of the Subject and then the Subject

FilePut(_FileNum, msg.Subject.Trim.Length)

FilePut(_FileNum, msg.Subject.Trim)

' Get the position of the start of the message in the disk file

msg.MessageStartPos = Seek(_FileNum)

msg.Size = msg.Message.Trim.Length * 2

' Save the length of the Message and then the Message

FilePut(_FileNum, msg.Message.Trim.Length)

FilePut(_FileNum, msg.Message.Trim)

FilePut(_FileNum, msg.Read)

FilePut(_FileNum, msg.Deleted)

End Sub

#End Region



Public Class NetworkListener ' Listens to the network

Public Class NetworkListener





' Public Events

Public Event IncomingMessage(ByVal Message As InstantMessage)

' Private Events

Private WithEvents Timer As New Timers.Timer(100)

' Private variables

Private TCPListener As Sockets.TcpListener

Private ListenerStarted As Boolean = False



#Region "Listener Public Properties"

' Returns the whether the Listener is started

Public ReadOnly Property IsRunning() As Boolean

Get

Return ListenerStarted

End Get

End Property

#End Region



#Region "Listener Private Methods"

' Initialise the Listener

Private Sub InitialiseListener(ByVal Port As Integer)

'LIP = GetLocalIP()

TCPListener = New Sockets.TcpListener(IPAddress.Any, Port)

End Sub



' Check for pending connections and process them

' This sub is called every Timer tick and checks if there are connections pending,

' if so a thread is started to process 1 request.

Private Sub CheckForPendingRequests(ByVal o As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles Timer.Elapsed

If TCPListener.Pending Then

Timer.Enabled = False

Dim ProcessRequest As New Threading.Thread(AddressOf ProcessConnectionRequest)

ProcessRequest.Start()

Timer.Enabled = True

End If

End Sub



' This sub processes each connection request (runs in a new thread)

Private Sub ProcessConnectionRequest()

' Socket returned by the TCPListener

Dim ClientConnection As System.Net.Sockets.TcpClient

Dim Msg As New InstantMessage

Dim LenBuffer(3) As Byte

Dim MessageLength As Integer

Dim Buffer() As Byte

Dim MessageChars() As Char

Dim strMessage As String

Try

ClientConnection = TCPListener.AcceptTcpClient

ClientConnection.ReceiveTimeout = 10000

' Get the length of the message

ClientConnection.GetStream.Read(LenBuffer, 0, LenBuffer.Length)

MessageLength = BitConverter.ToInt32(LenBuffer, 0)

' Get the message

ReDim Buffer(MessageLength - 1)

ClientConnection.GetStream.Read(Buffer, 0, Buffer.Length)

MessageChars = System.Text.Encoding.Default.GetChars(Buffer)

strMessage = New String(MessageChars, 0, MessageLength)

' Decode the received message

If strMessage.StartsWith("MESSAGE:") Then

DecodeEncodedMessage(strMessage.Substring(8), Msg)

End If

Catch ex As Exception

ClientConnection.Close()

Throw New Exception("Connection error")

'RaiseEvent DiagnosticMessage("Connection error")

End Try

' Return the message

ClientConnection.Close()

RaiseEvent IncomingMessage(Msg)



End Sub

#End Region



#Region "Listener Public Methods"

' Constructor

Public Sub New(ByVal Port As Integer, Optional ByVal AutoStart As Boolean = False)

InitialiseListener(Port)

If AutoStart Then StartListener()

End Sub

' Starts the Listener

Public Sub StartListener()

If Not ListenerStarted Then

TCPListener.Start()

Timer.Start()

Timer.Enabled = True

ListenerStarted = True

End If

End Sub

' Stops the Listener

Public Sub StopListener()

If ListenerStarted Then

Timer.Enabled = False

Timer.Stop()

TCPListener.Stop()

ListenerStarted = False

End If

End Sub

#End Region

End Class





Module Common ' Public variables are defined here

' Define Message Stores

Public Inbox As MessageStore

Public Sub InitialiseMessageStores()

' Open the message stores

Inbox = New MessageStore(Application.StartupPath & "\Inbox.box")

End Sub



Then the actual event handler that causes the error

Public Class MainForm  ' Windows form that starts the app

Private WithEvents NetListener As New NetworkListener(SystemPort)



' Handles incoming messages returned by the listerner NetListener

Public Sub NetListener_IncomingMessage(ByVal Message As InstantMessage) Handles NetListener.IncomingMessage

Inbox.AddMessage(Message)

End Sub

End Class

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The code is very long and I have removed most of the other code.