Android Code Snippet Check if an IP Address is Private or Public

Hi all,

this code check if an IP Addess is inside a private Local network, or Public otherwise.

I use it to restrict socket access to only local network on a safety situation where I control remotely with my app a 3D printer, CNC or Laser machines.

Here's the code:

' Check for Private network address
Sub IsPrivateIpAddress(ipStr As String) As Boolean

    Dim m As Matcher = Regex.Matcher("^(\d+)\.(\d+)\.(\d+)\.(\d+)$", ipStr)
    If m.Find = False Then
        Log("INVALID IP ADDRESS")
        Return False
    End If

    Select m.Group(1)
        Case 10
            If Not(inRange(m.Group(2), 0, 255)) Or Not(inRange(m.Group(3), 0, 255)) Or Not(inRange(m.Group(4), 0, 255)) Then Return False
            Return True  ' Class A: 10.0.0.0 to 10.255.255.255.
        Case 172
            If Not(inRange(m.Group(2), 16, 31)) Or Not(inRange(m.Group(3), 0, 255)) Or Not(inRange(m.Group(4), 0, 255)) Then Return False
            Return True   ' Class B: 172.16.0.0 to 172.31.255.255.
        Case 192
            If m.Group(2) <> 168 Or Not(inRange(m.Group(3), 0, 255)) Or Not(inRange(m.Group(4), 0, 255)) Then Return False
            Return True   ' Class C: 192.168.0.0 to 192.168.255.255.
        Case Else
            Return False
    End Select
End Sub

Sub inRange(num As Int, n1 As Int, n2 As Int) As Boolean
    Return num >= n1 And num <= n2
End Sub

This code should work on B4A, B4J, (I don't know B4i) and can be adapted to B4R.

Please if you see something wrong or you think it can be improved, feel free to post here your best solution.

I use it this way:

Sub btnRemoteConnect_Click
 
    If ServSock.GetMyWifiIP = "127.0.0.1" Then
        MsgboxAsync("This device is not connected with network. Please connect and try again.", " A T T E N T I O N")
'       Wait For MsgBox_Result (result As Int)
        Return
    End If
 
    Dim ip As String = txtIPAddress.Text.Trim
 
    If Settings.CNCType = Settings.TYPE_CNC_ROUTER Or Settings.CNCType = Settings.TYPE_CNC_LASER Then
        If Not(IsPrivateIpAddress(ip)) Then
            MsgboxAsync("FOR SAFETY REASONS, LASER and CNC Machines should only be controlled inside a Local Network" & CRLF & _
                        "and inside a same room where you remotely control it. This is not true for 3D printers.", " A T T E N T I O N")
'           Wait For MsgBox_Result (result As Int)
            Return
        End If
    End If
 
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