Socket non connesso e indirizzo non fornito durante l'invio

 Server.BeginReceive(Data, 0, Data.Length, SocketFlags.None, New AsyncCallback(AddressOf OnRecieve), Server)

Imports System.Net
Imports System.Net.Sockets

Public Class frmMain

    Dim ClientSock As Socket
    Dim ClientCount As Integer = 0
    Dim Data(1024) As Byte
    Dim Connected As Boolean = False

    Private Sub frmMain_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        pbConnected.Hide()
        pbDisconnected.Hide()
    End Sub

    Private Sub btnConnect_Click_1(sender As System.Object, e As System.EventArgs) Handles btnConnect.Click
        If Connected Then
            btnConnect.Enabled = False
        Else
            ClientSock = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
            Dim IPAddr As IPAddress = IPAddress.Parse("127.0.0.1")
            Dim IPEndPnt As IPEndPoint = New IPEndPoint(IPAddr, 8800)
            ClientSock.BeginConnect(IPEndPnt, New AsyncCallback(AddressOf OnConnect), Nothing)
            Connected = True
            ClientCount += 1
            pbConnected.Show()
            pbDisconnected.Hide()
        End If
    End Sub

    Private Sub OnConnect(ByVal Result As IAsyncResult)
        ClientSock.EndConnect(Result)
        ClientSock.BeginReceive(Data, 0, Data.Length, SocketFlags.None, New AsyncCallback(AddressOf OnRecieve), ClientSock)
    End Sub

    Private Sub OnRecieve(ByVal Result As IAsyncResult)
        Dim Client As Socket = Result.AsyncState
        Client.EndReceive(Result)
        Dim Received As Byte() = Data
        Dim Message As String = System.Text.ASCIIEncoding.ASCII.GetString(Received)
        Read(Message)
        Client.BeginReceive(Data, 0, Data.Length, SocketFlags.None, New AsyncCallback(AddressOf OnRecieve), ClientSock)
    End Sub

    Delegate Sub ReadMessage(ByVal Message As String)
    Private Sub Read(ByVal Message As String)
        If InvokeRequired Then
            Invoke(New ReadMessage(AddressOf Read), Message)
            Exit Sub
        End If
        If Message = "close" & ClientCount Then
            ClientSock.Close()
            pbConnected.Hide()
            pbDisconnected.Show()
        Else
            txtText.Text &= Message
        End If
    End Sub

    Private Sub frmMain_FormClosing(sender As System.Object, e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing
        If Connected Then
            Dim CloseBytesData() As Byte = System.Text.ASCIIEncoding.ASCII.GetBytes("close" & ClientCount)
            ClientSock.BeginSend(CloseBytesData, 0, CloseBytesData.Length, SocketFlags.None, New AsyncCallback(AddressOf OnSendCloseBytesData), Nothing)
            ClientSock.Close()
            pbConnected.Hide()
            pbDisconnected.Show()
        Else
            Application.Exit()
        End If
    End Sub

    Private Sub OnSendCloseBytesData(ByVal Result As IAsyncResult)
        Dim client As Socket = Result.AsyncState
        client.EndSend(Result)
        ClientCount = 0
    End Sub

    Private Sub btnDisconnect_Click(sender As System.Object, e As System.EventArgs) Handles btnDisconnect.Click
        Dim CloseBytesData() As Byte = System.Text.ASCIIEncoding.ASCII.GetBytes("close" & ClientCount)
        ClientSock.BeginSend(CloseBytesData, 0, CloseBytesData.Length, SocketFlags.None, New AsyncCallback(AddressOf OnSendCloseBytesData), Nothing)
        ClientSock.Close()
        pbConnected.Hide()
        pbDisconnected.Show()
    End Sub

    Private Sub ButtonExit_Click(sender As System.Object, e As System.EventArgs) Handles ButtonExit.Click
        Application.Exit()
    End Sub

    Private Sub MinimizeButton_Click(sender As System.Object, e As System.EventArgs) Handles MinimizeButton.Click
        Me.WindowState = FormWindowState.Minimized
    End Sub

End Class

Imports System.Net
Imports System.Net.Sockets

Public Class frmMain
    Dim Server As Socket
    Dim ClientCount As Integer = 0
    Dim ClientSock As Socket
    Dim Data(1024) As Byte

    Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Server = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
        Dim IpEndPoint As IPEndPoint = New IPEndPoint(IPAddress.Any, 8800)
        Server.Bind(IpEndPoint)
        Server.Listen(50)
        Server.BeginAccept(New AsyncCallback(AddressOf OnAccept), Nothing)
    End Sub

    Private Sub OnAccept(ByVal Result As IAsyncResult)
        ClientSock = Server.EndAccept(Result)
        Server.BeginAccept(New AsyncCallback(AddressOf OnAccept), Nothing)
        NewClient(ClientSock)
        ClientCount += 1
        Server.BeginReceive(Data, 0, Data.Length, SocketFlags.None, New AsyncCallback(AddressOf OnRecieve), Server)
    End Sub

    Private Sub OnRecieve(ByVal Result As IAsyncResult)
        Dim Client As Socket = Result.AsyncState
        Client.EndReceive(Result)
        Dim Received As Byte() = Data
        Dim Message As String = System.Text.ASCIIEncoding.ASCII.GetString(Received)
        Read(Message)
        Client.BeginReceive(Data, 0, Data.Length, SocketFlags.None, New AsyncCallback(AddressOf OnRecieve), Client)
    End Sub

    Delegate Sub ReadMessage(ByVal Message As String)
    Private Sub Read(ByVal Message As String)
        If InvokeRequired Then
            Invoke(New ReadMessage(AddressOf Read), Message)
            Exit Sub
        End If
        If Message = "close" & ClientCount Then
            lvClient.Items.RemoveAt(ClientCount - 1)
            Server.Close()
        Else
            Server.BeginAccept(New AsyncCallback(AddressOf OnAccept), Nothing)
        End If
    End Sub

    Delegate Sub AddNewClient(ByVal NewClient As Socket)
    Private Sub NewClient(ByVal Client As Socket)
        If InvokeRequired Then
            Invoke(New AddNewClient(AddressOf NewClient), Client)
            Exit Sub
        End If
        Dim ClientItem As New ListViewItem(Client.LocalEndPoint.ToString)
        ClientItem.Tag = Client
        lvClient.Items.Add(ClientItem)
    End Sub

    Private Sub SendMessageTo(ByVal Message As String, ByVal WichClient As Socket)
        Dim Bytes As Byte() = System.Text.ASCIIEncoding.ASCII.GetBytes(Message)
        WichClient.BeginSend(Bytes, 0, Bytes.Length, SocketFlags.None, New AsyncCallback(AddressOf OnSend), WichClient)
    End Sub

    Private Sub OnSend(ByVal Result As IAsyncResult)
        Dim client As Socket = Result.AsyncState
        client.EndSend(Result)
    End Sub

    Private Sub MenuSendMessage_Click(sender As System.Object, e As System.EventArgs) Handles SendMessage.Click
        For Each SingleClient As Object In lvClient.SelectedItems(0).Tag
            If SingleClient.Connected Then
                SendMessageTo("Message from server", lvClient.SelectedItems(0).Tag)
            Else
                MessageBox.Show("Can't send messate to this client because it's not connected", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
            End If
        Next
    End Sub

    Private Sub frmMain_FormClosing(sender As System.Object, e As System.Windows.Forms.FormClosingEventArgs) Handles MyBase.FormClosing
        Dim CloseBytesData() As Byte = System.Text.ASCIIEncoding.ASCII.GetBytes("close")
        For Each SingleClient As Socket In lvClient.Items
            SingleClient.BeginSend(CloseBytesData, 0, CloseBytesData.Length, SocketFlags.None, New AsyncCallback(AddressOf OnSendCloseBytesData), Nothing)
            SingleClient.Close()
        Next
        lvClient.Clear()
    End Sub

    Private Sub OnSendCloseBytesData(ByVal Result As IAsyncResult)
        Dim client As Socket = Result.AsyncState
        client.EndSend(Result)
    End Sub

    Private Sub ButtonExit_Click(sender As System.Object, e As System.EventArgs) Handles ButtonExit.Click
        Application.Exit()
    End Sub

    Private Sub ButtonMinimize_Click(sender As System.Object, e As System.EventArgs) Handles ButtonMinimize.Click
        Me.WindowState = FormWindowState.Minimized
    End Sub

End Class