Imports System

Imports System.Linq

Imports System.Net

Imports System.Net.Sockets

Public Module Module1

    Public Sub Main()

        Dim knownProxy = "127.0.0.1/8"

        Dim input As IPAddress

        IPAddress.TryParse("127.0.0.2", input)

        Dim parts As String() = knownProxy.Split("/")

        Dim maskAddress As IPAddress = IPAddress.Parse(parts(0))

​

        If maskAddress.AddressFamily <> input.AddressFamily Then

            'We got something like an IPV4-Address for an IPv6-Mask. This is not valid.

            Console.WriteLine("We got something like an IPV4-Address for an IPv6-Mask.")

        End If

​

        'A Subnetmask length should not be less than 0.

         If parts(1).Length <= 0 Then

            Console.WriteLine("A subnetmask length should not be less than 0.")

         End If

​

        If maskAddress.AddressFamily = AddressFamily.InterNetwork Then

             Console.WriteLine(String.Join(",", maskAddress.GetAddressBytes().Reverse().ToArray()))

             Dim maskAddressBits = BitConverter.ToUInt32(maskAddress.GetAddressBytes().Reverse().ToArray(), 0)

             Console.WriteLine(maskAddressBits)

             Dim ipAddressBits = BitConverter.ToUInt32(input.GetAddressBytes().Reverse().ToArray(), 0)

             Console.WriteLine(ipAddressBits)

             Dim prefixLength As Integer

             Integer.TryParse(parts(1), prefixLength)

             Dim mask = UInt32.MaxValue << (32 - prefixLength)

             Console.WriteLine(maskAddressBits.GetType())

             Console.WriteLine(mask.GetType())

             Dim badBitwiseAndResult = (maskAddressBits & mask)

             Console.WriteLine(badBitwiseAndResult.GetType())

             Console.WriteLine(badBitwiseAndResult)

             If (maskAddressBits & mask) = (ipAddressBits & mask) Then

                Console.WriteLine("It matches with the original code")

             End If

             Dim goodBitwiseAndResult = (maskAddressBits AND mask)

             Console.WriteLine(goodBitwiseAndResult.GetType())

             Console.WriteLine(goodBitwiseAndResult)

             If (maskAddressBits AND mask) = (ipAddressBits AND mask) Then

                Console.WriteLine("It matches by changing the AND operator")

             End If

         End If

        Console.WriteLine("Ending.")

    End Sub

End Module