Error?? TcpListener

Hi There,

I have nearly finished my network file transfer program, but I am getting the following error when I try to send a file to the server,

Invalid Cast Exception was handled
Unable to cast object of type "System.Int32" to type "System/net/Sockets.TCPListener".

Here is my code:

Code:

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Imports System.Net
Imports System.Net.Sockets
Imports Microsoft.Win32

Public Class Main
    Private listen As Threading.Thread

    Private Sub Status_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Status.Tick
        If ToolStripStatusLabel1.Text = "Server Running" Then
            ToolStripStatusLabel1.ForeColor = Color.Green
        ElseIf ToolStripStatusLabel1.Text = "Server Error!" Then
            ToolStripStatusLabel1.ForeColor = Color.Red
        End If
        TextBox1.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset1.txt")
        TextBox2.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset2.txt")
        TextBox3.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset3.txt")
        TextBox4.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset4.txt")
    End Sub
    Sub listener()
        Dim l As New TcpListener(Net.IPAddress.Any, 8080)
        l.Start()
        Do
            If l.Pending Then l.BeginAcceptTcpClient(AddressOf accepting, 1)
            Threading.Thread.Sleep(10000)
        Loop
    End Sub
    Sub accepting(ByVal ar As IAsyncResult)
        'receives filename, filelength, filebytes
        Dim listener As TcpListener = CType(ar.AsyncState, TcpListener)
        Dim clientSocket As TcpClient = listener.EndAcceptTcpClient(ar)
        Dim filename, filepath As String, filelen As Long
        'using binaryreader (wrapped networkstream) to read a String and a Long
        Dim br As New IO.BinaryReader(clientSocket.GetStream)
        filename = br.ReadString
        filelen = br.ReadInt64
        'filepath = IO.Path.Combine(Application.StartupPath, filename)

        If filename.Contains(".wav") Then
            filepath = ("C:\remote Audio\Audio\Audio.wav")
        Else
            filepath = IO.Path.Combine("C:\remote Audio\Audio", filename)
        End If
        Dim buffer(8092) As Byte, readstotal As Long = 0
        Dim reads As Integer = -1
        'using filestream to write read filebytes directly from networkstream
        Using fs As New IO.FileStream(filepath, IO.FileMode.Create, IO.FileAccess.Write)
            Do Until readstotal = filelen
                reads = clientSocket.GetStream.Read(buffer, 0, buffer.Length)
                fs.Write(buffer, 0, reads)
                readstotal += reads
            Loop
        End Using
    End Sub

    Private Sub Main_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        System.Diagnostics.Process.GetCurrentProcess.Kill()
    End Sub
    Private Sub Main_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        listen = New Threading.Thread(AddressOf listener)
        listen.Start()
        ToolStripStatusLabel1.Text = "Server Running"
        Try
        Catch ex As Exception
            ToolStripStatusLabel1.Text = "Server Error!"
        End Try
        TextBox1.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset1.txt")
        TextBox2.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset2.txt")
        TextBox3.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset3.txt")
        TextBox4.Text = My.Computer.FileSystem.ReadAllText("C:\Remote Audio\Data\Preset4.txt")
    End Sub

    Private Sub Audio_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Audio.Tick
        Try
            If My.Computer.FileSystem.FileExists("C:\remote Audio\Audio\Audio.wav") Then
                Audio_Play.start()
            End If
        Catch ex As Exception
            Audio_Error.SetError(Me, "Invalid Audio File!")
        End Try
       
    End Sub

    Private Sub Audio_Play_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Audio_Play.Tick
        Try
            My.Computer.Audio.Play("C:\Remote Audio\Audio\Audio.wav", AudioPlayMode.WaitToComplete)
            My.Computer.FileSystem.DeleteFile("C:\remote Audio\Audio\Audio.wav")
        Catch ex As Exception
            MsgBox("Invalid Audio file!", MsgBoxStyle.Critical, "Error")
            Audio_Error.SetError(Me, "Invalid Audio File!")
        End Try
    End Sub

    Private Sub RunInBackgroundToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RunInBackgroundToolStripMenuItem.Click
        Me.Hide()
    End Sub

    Private Sub NotifyIcon1_MouseDoubleClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles NotifyIcon1.MouseDoubleClick
        Me.Show()

    End Sub

    Private Sub Preset_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Preset_Status.Tick
        If My.Computer.FileSystem.FileExists("C:\remote audio\audio\preset1.txt") Then
            Label1.ForeColor = Color.Red
            Label1.Text = "Preparing to Play Preset 1"
            Preset1.Start()
        ElseIf My.Computer.FileSystem.FileExists("C:\remote audio\audio\preset2.txt") Then
            Label1.ForeColor = Color.Red
            Label1.Text = "Preparing to Play Preset 2"
            Preset2.Start()
        ElseIf My.Computer.FileSystem.FileExists("C:\remote audio\audio\preset3.txt") Then
            Label1.ForeColor = Color.Red
            Label1.Text = "Preparing to Play Preset 3"
            Preset3.Start()
        ElseIf My.Computer.FileSystem.FileExists("C:\remote audio\audio\preset4.txt") Then
            Label1.ForeColor = Color.Red
            Label1.Text = "Preparing to Play Preset 4"
            Preset4.Start()
        Else
            Label1.ForeColor = Color.Green
            Label1.Text = "Waiting for Client"
        End If

    End Sub

    Private Sub Preset1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Preset1.Tick
        Try
            My.Computer.Audio.Play(My.Resources.vchord_g7, AudioPlayMode.WaitToComplete)
            My.Computer.Audio.Play(TextBox1.Text, AudioPlayMode.WaitToComplete)
            My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset1.txt")
            Preset1.Stop()
        Catch ex As Exception
            If My.Computer.FileSystem.FileExists("C:\Remote Audio\Audio\Preset2.txt") = True Then
                My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset2.txt")
                MsgBox("Error! Cannot Play Preset 2!" & vbNewLine & vbNewLine & "File does not exist or is invalid.", MsgBoxStyle.Critical, "Error")
            End If
        End Try
    End Sub

    Private Sub PresetAudioSettingsToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PresetAudioSettingsToolStripMenuItem.Click
        Preset.ShowDialog()
    End Sub

    Private Sub Preset2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Preset2.Tick
        Try
            My.Computer.Audio.Play(My.Resources.vchord_g7, AudioPlayMode.WaitToComplete)
            My.Computer.Audio.Play(TextBox2.Text, AudioPlayMode.WaitToComplete)
            My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset2.txt")
            Preset2.Stop()
        Catch ex As Exception
            If My.Computer.FileSystem.FileExists("C:\Remote Audio\Audio\Preset2.txt") = True Then
                My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset2.txt")
                MsgBox("Error! Cannot Play Preset 2!" & vbNewLine & vbNewLine & "File does not exist or is invalid.", MsgBoxStyle.Critical, "Error")
            End If
        End Try
    End Sub

    Private Sub Preset3_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Preset3.Tick
        Try
            My.Computer.Audio.Play(My.Resources.vchord_g7, AudioPlayMode.WaitToComplete)
            My.Computer.Audio.Play(TextBox3.Text, AudioPlayMode.WaitToComplete)
            My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset3.txt")
            Preset3.Stop()
        Catch ex As Exception
            If My.Computer.FileSystem.FileExists("C:\Remote Audio\Audio\Preset3.txt") = True Then
                My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset3.txt")
                MsgBox("Error! Cannot Play Preset 3!" & vbNewLine & vbNewLine & "File does not exist or is invalid.", MsgBoxStyle.Critical, "Error")
            End If
        End Try
    End Sub

    Private Sub Preset4_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Preset4.Tick
        Try
            My.Computer.Audio.Play(My.Resources.vchord_g7, AudioPlayMode.WaitToComplete)
            My.Computer.Audio.Play(TextBox4.Text, AudioPlayMode.WaitToComplete)
            My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset4.txt")
            Preset4.Stop()
        Catch ex As Exception
            If My.Computer.FileSystem.FileExists("C:\Remote Audio\Audio\Preset4.txt") = True Then
                My.Computer.FileSystem.DeleteFile("C:\Remote Audio\Audio\Preset4.txt")
                MsgBox("Error! Cannot Play Preset 4!" & vbNewLine & vbNewLine & "File does not exist or is invalid.", MsgBoxStyle.Critical, "Error")
            End If
        End Try
    End Sub

    Private Sub StatusStrip1_ItemClicked(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ToolStripItemClickedEventArgs) Handles StatusStrip1.ItemClicked

    End Sub
End Class

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Thanks!

Josh

There's a lot of code there and there's no reason that we should have waste our time searching through it all looking for a possible place that that exception is thrown when you could simply tell us exactly where the exception is thrown. Help us to help and you're much more likely to get a solution.

Hi,

The error comes up here

Code:

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Dim listener As TcpListener = CType(ar.AsyncState, TcpListener)

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Thanks,

Josh

When you call BeginAcceptTcpClient, whatever you pass to the 'state' parameter is what you get back from the ar.AsyncState property inside the callback. Have a look at where you're calling BeginAcceptTcpClient and what you're passing as an argument. I think I can see why you made the mistake and, if I'm right, it should encourage you to use more descriptive variable names in future.

Can you please explain better?

It's quite simple. You get get back (the value of ar.AsyncState) whatever you pass in (the second argument to BeginAcceptTcpClient). You are obviously expecting to get back a TcpListener so you would have to be passing in a TcpListener in the first place. Are you doing that? Obviously not, or you wouldn't be getting that error message. The error message says that it's failing to cast an Int32 as type TcpListener, so you must be passing in an Int32.

So what would the basic steps be to fixing this? :)
As I'm only a student learning vb.

Thanks.

Have you actually identified where the problem is? Have you done what I said? Can you actually show me where the error is, or are you just waiting for me to tell you what to do? If you're capable of writing a network file transfer program using asynchronous methods then you should be able to follow my instructions to identify where the problem is, what the problem is and what to do to fix it.

Hi,

Yes, and I think it might be fixed, after doing some checks.
I found that I had put a 1 instead of a L, as they look very simular in VB.

It was this part of the code:

Code:

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If l.Pending Then l.BeginAcceptTcpClient(AddressOf accepting, l)

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Thanks!

Josh

Quote:

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Originally Posted by josh133

I found that I had put a 1 instead of a L, as they look very simular in VB.

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Exactly. Hopefully you feel better for having found it yourself, albeit with a little help. It is always my intention to get the poster to do as much as they can for themselves because they learn more that way. As for this:

Quote:

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if I'm right, it should encourage you to use more descriptive variable names in future.

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The implication was that you would not have made that mistake if you had used a descriptive variable name like 'listener'.

Thanks Again! :D