UDP Multicast Chat

Imports System.Net.Sockets
Imports System.Runtime.InteropServices

Public Class Form1
    <DllImport("user32.dll", EntryPoint:="FlashWindow")> _
    Public Shared Function FlashWindow(ByVal hwnd As Integer, ByVal bInvert As Integer) As Integer
    End Function

    Dim mCast As New UdpClient(4446)
    Dim ep As Net.IPEndPoint = New Net.IPEndPoint(Net.IPAddress.Parse("230.0.0.1"), 4446)
    Dim ep2 As Net.IPEndPoint = New Net.IPEndPoint(Net.IPAddress.Parse("230.0.0.1"), 4446)
    Dim KAFlags As New List(Of Boolean)
    Dim KAcheck As Integer = 0
    Dim mycomputerconnections() As Net.NetworkInformation.NetworkInterface

    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        Try
            If mCast.Client.Connected = True Then
                Dim sendbytes() As Byte = System.Text.Encoding.ASCII.GetBytes(TextBox1.Text & ": :Disconnect")
                mCast.Send(sendbytes, sendbytes.Length, ep)
                mCast.Close()
            End If
        Catch ex As Exception
        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        mCast.Client.ReceiveTimeout = 100
        mCast.Client.Blocking = False
        mCast.MulticastLoopback = False
        Dim AddressString As String = ""
        For i = 0 To mycomputerconnections(ComboBox1.SelectedIndex).GetIPProperties.UnicastAddresses.Count - 1

            If mycomputerconnections(ComboBox1.SelectedIndex).GetIPProperties.UnicastAddresses(i).Address.AddressFamily = Net.Sockets.AddressFamily.InterNetwork Then

                Dim bytez() As Byte = mycomputerconnections(ComboBox1.SelectedIndex).GetIPProperties.UnicastAddresses(i).Address.GetAddressBytes
                AddressString = bytez(0) & "." & bytez(1) & "." & bytez(2) & "." & bytez(3)
                Exit For
            End If
        Next

        mCast.JoinMulticastGroup(Net.IPAddress.Parse("230.0.0.1"), Net.IPAddress.Parse(AddressString))
        mCast.Client.EnableBroadcast = True
        Dim sendbytes() As Byte = System.Text.Encoding.ASCII.GetBytes(TextBox1.Text & ": :Connect")
        ListBox1.Items.Add(TextBox1.Text)
        mCast.Send(sendbytes, sendbytes.Length, ep)
        Timer1.Enabled = True
        Timer2.Enabled = True
        Button2.Enabled = True
        Button3.Enabled = True
        Button1.Enabled = False
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim sendbytes() As Byte = System.Text.Encoding.ASCII.GetBytes(TextBox1.Text & ": :Disconnect")
        mCast.Send(sendbytes, sendbytes.Length, ep)
        mCast.Close()
        Timer1.Enabled = False
        Timer2.Enabled = False
        Button2.Enabled = False
        Button3.Enabled = False
        Button1.Enabled = True
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Try
            Dim rcvbytes() As Byte = mCast.Receive(ep2)
            Dim MCSubRcv As String = System.Text.Encoding.ASCII.GetString(rcvbytes)

            If MCSubRcv <> "" And MCSubRcv.Contains(":Chat") Then
                RichTextBox1.AppendText(MCSubRcv.Split(":")(0) & ": " & MCSubRcv.Split(":")(1) & Chr(13))
                RichTextBox1.SelectionStart = RichTextBox1.TextLength
                RichTextBox1.ScrollToCaret()
                If Me.Focused = False Then
                    FlashWindow(Me.Handle, 1)
                End If
            End If
            If MCSubRcv <> "" And MCSubRcv.Contains(":Disconnect") = True Then
                ListBox1.Items.RemoveAt(MCSubRcv.Split(":")(0))
            End If

            If MCSubRcv <> "" And MCSubRcv.Contains(":KeepAlive") = True Then
                If ListBox1.Items.Count > 0 Then
                    Dim found As Boolean = False
                    For i = 0 To ListBox1.Items.Count - 1
                        If ListBox1.Items(i) = MCSubRcv.Split(":")(0) Then
                            found = True
                            KAFlags(i - 1) = True
                        End If
                    Next
                    If found = False Then
                        ListBox1.Items.Add(MCSubRcv.Split(":")(0))
                        KAFlags.Add(True)
                    End If
                Else
                    ListBox1.Items.Add(MCSubRcv.Split(":")(0))
                    KAFlags.Add(True)
                End If
            End If
        Catch ex As Exception
        End Try
    End Sub

    Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick
        Dim sendbytes() As Byte = System.Text.Encoding.ASCII.GetBytes(TextBox1.Text & ": :" & "KeepAlive")
        mCast.Send(sendbytes, sendbytes.Length, ep)
        If KAcheck >= 4 Then
            For i = 0 To KAFlags.Count - 1
                If KAFlags(i) = False Then
                    ListBox1.Items.RemoveAt(i + 1)
                    KAFlags.RemoveAt(i)
                    Exit For
                End If
            Next
            KAcheck = 0
            For i = 0 To KAFlags.Count - 1
                KAFlags(i) = False
            Next
        Else
            KAcheck = KAcheck + 1
        End If

    End Sub

    'Send Chat
    Private Sub TextBox2_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox2.KeyDown
        If e.KeyCode = Keys.Enter Then
            sendz()
        End If
    End Sub
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        sendz()
    End Sub
    Private Sub sendz()
        Dim sendbytes() As Byte = System.Text.Encoding.ASCII.GetBytes(TextBox1.Text & ":" & TextBox2.Text & ":" & "Chat")
        mCast.Send(sendbytes, sendbytes.Length, ep)
        RichTextBox1.AppendText("Me: " & TextBox2.Text & Chr(13))
        RichTextBox1.SelectionStart = RichTextBox1.TextLength
        RichTextBox1.ScrollToCaret()
        TextBox2.Text = ""
    End Sub

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        mycomputerconnections = Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces
        For i = 0 To mycomputerconnections.Length - 1
            ComboBox1.Items.Add(mycomputerconnections(i).Name)
        Next
        ComboBox1.SelectedIndex = 0
    End Sub
End Class