在 vb.net 中将子网掩码转换为二进制（八位字节）

Question

如何将子网掩码转换为二进制，以便最终得到 32 位数字？

我可以使用 Convert.ToString(Long-to-convert, 2) 将其转换为二进制，

但返回 255.255.255.0 的子网掩码（但它返回时不带空格）：

1111 1111 1111 1111 1111 1111 0

当我想要它时是：

1111 1111 1111 1111 1111 1111 0000 0000

Answer 1

如果单独转换每个字节，那么在连接步骤之前，您可以对每个值执行 PadLeft(8, '0') 。这将添加缺失的“0”。

Answer 2

'place this code in a separate module
'originally written by Dewayne Basnett in VBA - 1997
'converted to VB .Net - 2007
Option Strict On : Option Explicit On : Option Infer Off
Imports System.Net, System.Text
Module IP4Stuff
    Const IPbrdcst As Long = 4294967295 '255.255.255.255   FF.FF.FF.FF
    Dim aIP, aMSK As IPAddress
    Dim nIP, nMSK, nNET, nHOST, addrs As Long 'numeric equivalents
    Dim nCIDR, CIDR, x, y As Integer

    Const shBits As Boolean = True 'True = show debug with bits using showBits function
    Public Function ipRange(ByVal ipAddr As String, _
                            ByVal ipMask As String) As List(Of String)
        'returns a list of all ip addresse on a given network
        '
        'ipRange("192.168.3.133", "255.255.254.0") '512 hosts - octet crossing
        '
        '255.255.254.0 is /23
        'List(Of String) - partial output
        '192.168.2.0
        '192.168.2.1
        '192.168.2.2
        '...
        '192.168.2.254
        '192.168.2.255
        '192.168.3.0
        '192.168.3.1
        '...
        '192.168.3.253
        '192.168.3.254
        '192.168.3.255         
        'note
        'first entry in list is THE network number
        'last entry in list is the directed broadcast
        '
        nMSK = IPasNum(ipMask) 'get the Mask as number
        CIDR = nCIDR 'get CIDR
        nIP = IPasNum(ipAddr) 'get the IP address as number
        nNET = IPnetAsNum(nIP, nMSK) 'get THE network number as number
        addrs = nNET 'addrs = THE network number as number 
        nHOST = IPnumOfHosts(nMSK) 'get the number of hosts

        If shBits Then
            Debug.WriteLine("")
            Debug.WriteLine("IP".PadRight(10, " "c) & showBits(nIP) & " " & ipAddr)
            Debug.WriteLine("Mask".PadRight(10, " "c) & showBits(nMSK) & " " & ipMask)
            Debug.WriteLine("Net".PadRight(10, " "c) & showBits(nNET) & " " & NumToIp(nNET))
            Debug.WriteLine("Hosts".PadRight(10, " "c) & showBits(nHOST) & " " & nHOST.ToString)
            Debug.WriteLine("CIDR".PadRight(10, " "c) & CIDR.ToString)
            'Stop
        End If

        If nIP < 0 OrElse nMSK < 0 OrElse nNET = 0 OrElse nHOST = 0 Then
            Return New List(Of String) 'error
        End If
        ipRange = New List(Of String)
        For x As Long = 0 To nHOST
            ipRange.Add(NumToIp(addrs)) 'add host to list
            addrs += 1 'increment it
        Next
    End Function

    Public Function IPnets(ByVal ipAddr As String, _
                           ByVal curCIDR As Integer, _
                           ByVal newCIDR As Integer) As List(Of String)
        'returns a list of sub-nets using any IP in the current network,
        'the current mask as CIDR and new mask as CIDR.
        '192.168.3.? /23 to /25 - octet crossing
        '
        'IPnets("192.168.3.128", 23, 25)
        '
        'List(Of String)
        '255.255.255.128
        '192.168.2.0
        '192.168.2.128
        '192.168.3.0
        '192.168.3.128
        '
        Dim curMASK, newMASK, netPlus1 As Long, numOfNets As Integer
        nIP = IPasNum(ipAddr) 'get the IP address as number
        If nIP < 0 OrElse curCIDR < 2 OrElse curCIDR > newCIDR OrElse newCIDR > 30 Then
            Return New List(Of String) 'error
        End If
        IPnets = New List(Of String)
        curMASK = MaskFromCidr(curCIDR) 'convert CIDR's to mask as number
        newMASK = MaskFromCidr(newCIDR)
        nHOST = IPnumOfHosts(newMASK)
        netPlus1 = nHOST + 1 'used to add 1 to the network portion of the ip address
        nNET = IPnetAsNum(nIP, curMASK) 'get THE network number as number
        numOfNets = CInt(2 ^ (newCIDR - curCIDR)) 'number of networks
        IPnets.Add(NumToIp(newMASK)) '<<<<<<<<<<<<<<<<<<<<< first entry in list is the new mask

        If shBits Then
            Debug.WriteLine("")
            Debug.WriteLine("IP".PadRight(10, " "c) & showBits(nIP) & " " & ipAddr)
            Debug.WriteLine("Network".PadRight(10, " "c) & showBits(nNET) & " " & NumToIp(nNET))
            Debug.WriteLine("Cur. Mask".PadRight(10, " "c) & showBits(curMASK) & " " & NumToIp(curMASK))
            Debug.WriteLine("New Mask".PadRight(10, " "c) & showBits(newMASK) & " " & NumToIp(newMASK))
            Debug.WriteLine("Plus 1".PadRight(10, " "c) & showBits(netPlus1) & " " & NumToIp(netPlus1))
            Debug.WriteLine("Num. Nets".PadRight(10, " "c) & numOfNets.ToString)
            'Stop
        End If

        For x As Integer = 0 To numOfNets - 1
            IPnets.Add(NumToIp(nNET))
            'to get last address(broadcast) Dim BrdCst as long = nNET Or nHOST
            nNET += netPlus1 'add one network number
        Next
    End Function

    Private Function MaskFromCidr(ByVal CIDR As Integer) As Long
        'x = 32 - CIDR
        'z = (2^x)-1
        'return z xor 255.255.255.255
        MaskFromCidr = CLng(2 ^ ((32 - CIDR)) - 1) Xor IPbrdcst
    End Function

    Private Function IPnumOfHosts(ByVal IPmsk As Long) As Long 'a mask for the host portion
        '255.255.255.0 XOR 255.255.255.255 = 255 so 0 to 255 is 256 hosts
        IPnumOfHosts = IPmsk Xor IPbrdcst 'cacluate the number of hosts
    End Function

    Private Function IPnetAsNum(ByVal IPnum As Long, ByVal IPmsk As Long) As Long 'extract network from ip address
        '192.168.2.113 AND 255.255.255.0 = 192.168.2.0
        IPnetAsNum = IPnum And IPmsk 'calculate THE network number
    End Function

    Private Function IPasNum(ByVal AipAddr As String) As Long 'return -1 on error
        If Not IPAddress.TryParse(AipAddr, aIP) Then 'convert string to IP
            Return -1 'error
        Else
            IPasNum = IPtoNum(aIP) 'convert IP to number
            If IPasNum = 0 Then
                Return -1 'error
            End If
        End If
    End Function
    Private Function IPtoNum(ByVal theIP As IPAddress) As Long 'convert IP to number
        Dim IPb() As Byte = theIP.GetAddressBytes 'get the octets
        Dim theBit As Integer = 31 'work MSb to LSb
        Dim addr As Long 'accumulator for address
        nCIDR = 0
        For x = 0 To 3 'four octets
            For y = 7 To 0 Step -1 'with 8 bits each - duh
                If (IPb(x) And CByte(2 ^ y)) = CByte(2 ^ y) Then 'if the bit is on
                    addr += CLng(2 ^ theBit) 'accumulate
                    nCIDR += 1 'count bits
                End If
                theBit -= 1 'decrement bit pos
            Next
        Next
        Return addr
    End Function
    Private Function NumToIp(ByVal theIP As Long) As String 'convert number back to IP
        Dim IPb(3) As Byte '4 octets
        Dim theBit As Integer = 31 'work MSb to LSb
        Dim addr As String 'accumulator for address
        For x = 0 To 3 'four octets
            For y = 7 To 0 Step -1 '8 bits
                If (theIP And CLng(2 ^ theBit)) = CLng(2 ^ theBit) Then 'if the bit is on
                    IPb(x) += CByte(2 ^ y) 'accumulate
                End If
                theBit -= 1
            Next
            addr &= IPb(x).ToString & "." 'add current octet to string
        Next
        Return addr.TrimEnd("."c)
    End Function
    Private Function showBits(ByVal aNum As Long) As String
        Dim strObits As New StringBuilder
        strObits.Append(Convert.ToString(aNum, 2).PadLeft(32, "0"c))
        For ix As Integer = 24 To 0 Step -8
            strObits.Insert(ix, " ")
        Next
        showBits = strObits.ToString.Trim
    End Function
End Module