Option Explicit On

Imports System.IO
Imports System.Net
Imports System.Net.Sockets

Public Class Form1

    Dim _socket As Socket
    Dim bindEndpoint As IPEndPoint
    Private byteData As Byte() = New Byte(4095) {}
    Dim bContinueCapturing As Boolean = False


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        bContinueCapturing = True
        '_socket.BeginReceive(byteData, 0, byteData.Length, SocketFlags.None, New AsyncCallback(AddressOf OnReceive), Nothing)
    End Sub

    Private Sub Form1_Disposed(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Disposed
        _socket.Close()
    End Sub

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        _socket = New Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP)
        bindEndpoint = New IPEndPoint(IPAddress.Parse(Dns.GetHostByName(Dns.GetHostName).AddressList(0).ToString), 0)
        _socket.Bind(bindEndpoint)
        _socket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.HeaderIncluded, True)

        Dim byTrue As Byte() = New Byte(3) {1, 0, 0, 0}
        Dim byOut As Byte() = New Byte(3) {1, 0, 0, 0}
        _socket.IOControl(IOControlCode.ReceiveAll, byTrue, byOut)
    End Sub

    Private Sub OnReceive(ByVal ar As IAsyncResult)
        Try
            If bContinueCapturing Then
                Dim nReceived As Integer = _socket.EndReceive(ar)

                ParseData(byteData, nReceived)

                byteData = New Byte(4095) {}
                _socket.BeginReceive(byteData, 0, byteData.Length, SocketFlags.None, New AsyncCallback(AddressOf OnReceive), Nothing)
            End If
        Catch ex As ObjectDisposedException
            Trace.WriteLine("OnReceive->ObjectDisposedException: " & ex.Message)
        Catch ex As Exception
            Trace.WriteLine("OnReceive->Exception: " & ex.Message)
        End Try
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        bContinueCapturing = False
    End Sub

    Private Sub ParseData(ByVal byteData As Byte(), ByVal nReceived As Integer)

        Dim ipHeader As New IPHeader(byteData, nReceived)

        Trace.WriteLine(ipHeader.SourceAddress.ToString & " => " & ipHeader.DestinationAddress.ToString)

        Select Case ipHeader.ProtocolType
            Case Protocol.TCP
                Dim tcpHeader As New TCPHeader(ipHeader.Data, ipHeader.MessageLength)

                If tcpHeader.DestinationPort = "53" OrElse tcpHeader.SourcePort = "53" Then
                    Dim dnsHeader As New DNSHeader(tcpHeader.Data, tcpHeader.MessageLength)
                    ' DNS
                End If
            Case Protocol.UDP
                Dim udpHeader As New UDPHeader(ipHeader.Data, CInt(ipHeader.MessageLength))

                If udpHeader.DestinationPort = "53" OrElse udpHeader.SourcePort = "53" Then
                    ' DNS
                    Dim dnsHeader As New DNSHeader(udpHeader.Data, udpHeader.Length)
                End If
            Case Protocol.Unknown
                ' TODO
        End Select
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim encoding As New System.Text.UTF8Encoding()
        _socket.SendTo(encoding.GetBytes("abcabcabc"), bindEndpoint)
    End Sub
End Class