C# Signature:
[DllImport("iphlpapi.dll", EntryPoint="GetIpNetTable")]
static extern int GetIpNetTable(IntPtr pIpNetTable, ref int pdwSize, bool bOrder);
VB.NET Signature:
<DllImport("IpHlpApi.dll")>
Private Shared Function GetIpNetTable(pIpNetTable As IntPtr, <MarshalAs(UnmanagedType.U4)> ByRef pdwSize As Integer, bOrder As Boolean) As <MarshalAs(UnmanagedType.U4)> Integer
End Function
C# User-Defined Types:
// Define the MIB_IPNETROW structure.
[StructLayout(LayoutKind.Sequential)]
struct MIB_IPNETROW
{
[MarshalAs(UnmanagedType.U4)]
public uint dwIndex;
[MarshalAs(UnmanagedType.U4)]
public uint dwPhysAddrLen;
[MarshalAs(UnmanagedType.U1)]
public byte mac0;
[MarshalAs(UnmanagedType.U1)]
public byte mac1;
[MarshalAs(UnmanagedType.U1)]
public byte mac2;
[MarshalAs(UnmanagedType.U1)]
public byte mac3;
[MarshalAs(UnmanagedType.U1)]
public byte mac4;
[MarshalAs(UnmanagedType.U1)]
public byte mac5;
[MarshalAs(UnmanagedType.U1)]
public byte mac6;
[MarshalAs(UnmanagedType.U1)]
public byte mac7;
[MarshalAs(UnmanagedType.U4)]
public uint dwAddr;
[MarshalAs(UnmanagedType.U4)]
public uint dwType;
}
VB.NET User-Defined Types:
Public Const ERROR_SUCCESS As Integer = 0
Public Const ERROR_INSUFFICIENT_BUFFER As Integer = 122
<StructLayout(LayoutKind.Sequential)>
Public Structure MIB_IPNETROW
<MarshalAs(UnmanagedType.U4)>
Public dwIndex As UInteger
<MarshalAs(UnmanagedType.U4)>
Public dwPhysAddrLen As UInteger
<MarshalAs(UnmanagedType.ByValArray, SizeConst:=6)>
Public bPhysAddr() As Byte
<MarshalAs(UnmanagedType.U4)>
Public dwAddr As UInteger
<MarshalAs(UnmanagedType.U4)>
Public dwType As DWTYPES
End Structure
Public Enum DWTYPES As UInteger
<MarshalAs(UnmanagedType.U4)>
Other = 1
<MarshalAs(UnmanagedType.U4)>
Invalid = 2
<MarshalAs(UnmanagedType.U4)>
Dynamic = 3
<MarshalAs(UnmanagedType.U4)>
[Static] = 4
End Enum
Alternative Managed API:
Do you know one? Please contribute it!
Notes:
If you are only interesting in getting the mac Address and you are deploying to Windows 2008 or later, you might want to use ResolveIpNetEntry2 (http://msdn.microsoft.com/en-us/library/aa814455(VS.85).aspx) instead.
Tips & Tricks:
Please add some!
C# Sample Code:
//http://stackoverflow.com/questions/1148778/how-do-i-access-arp-protocol-information-through-c-net
using System;
using System.Runtime.InteropServices;
using System.ComponentModel;
using System.Net;
namespace GetIpNetTable
{
class Program {
// The max number of physical addresses.
const int MAXLEN_PHYSADDR = 8;
// Declare the GetIpNetTable function.
[DllImport("IpHlpApi.dll")]
[return: MarshalAs(UnmanagedType.U4)]
static extern int GetIpNetTable(
IntPtr pIpNetTable,
[MarshalAs(UnmanagedType.U4)]
ref int pdwSize,
bool bOrder);
// The insufficient buffer error.
const int ERROR_INSUFFICIENT_BUFFER = 122;
static void Main(string[] args)
{
// The number of bytes needed.
int bytesNeeded = 0;
// The result from the API call.
int result = GetIpNetTable(IntPtr.Zero, ref bytesNeeded, false);
// Call the function, expecting an insufficient buffer.
if (result != ERROR_INSUFFICIENT_BUFFER)
{
// Throw an exception.
throw new Win32Exception(result);
}
// Allocate the memory, do it in a try/finally block, to ensure
// that it is released.
IntPtr buffer = IntPtr.Zero;
// Try/finally.
try
{
// Allocate the memory.
buffer = Marshal.AllocCoTaskMem(bytesNeeded);
// Make the call again. If it did not succeed, then
// raise an error.
result = GetIpNetTable(buffer, ref bytesNeeded, false);
// If the result is not 0 (no error), then throw an exception.
if (result != 0)
{
// Throw an exception.
throw new Win32Exception(result);
}
// Now we have the buffer, we have to marshal it. We can read
// the first 4 bytes to get the length of the buffer.
int entries = Marshal.ReadInt32(buffer);
// Increment the memory pointer by the size of the int.
IntPtr currentBuffer = new IntPtr(buffer.ToInt64() +
Marshal.SizeOf(typeof(int)));
// Allocate an array of entries.
MIB_IPNETROW[] table = new MIB_IPNETROW[entries];
// Cycle through the entries.
for (int index = 0; index < entries; index++)
{
// Call PtrToStructure, getting the structure information.
table[index] = (MIB_IPNETROW) Marshal.PtrToStructure(new
IntPtr(currentBuffer.ToInt64() + (index *
Marshal.SizeOf(typeof(MIB_IPNETROW)))), typeof(MIB_IPNETROW));
}
for (int index = 0; index < entries; index++)
{
IPAddress ip=new IPAddress(table[index].dwAddr);
Console.Write("IP:"+ip.ToString()+"\t\tMAC:");
byte b;
b=table[index].mac0;
if ( b < 0x10)
{
Console.Write("0");
}
else
{
Console.Write("");
}
Console.Write(b.ToString("X"));
b=table[index].mac1;
if ( b < 0x10)
{
Console.Write("-0");
}
else
{
Console.Write("-");
}
Console.Write(b.ToString("X"));
b=table[index].mac2;
if ( b < 0x10)
{
Console.Write("-0");
}
else
{
Console.Write("-");
}
Console.Write(b.ToString("X"));
b=table[index].mac3;
if ( b < 0x10)
{
Console.Write("-0");
}
else
{
Console.Write("-");
}
Console.Write(b.ToString("X"));
b=table[index].mac4;
if ( b < 0x10)
{
Console.Write("-0");
}
else
{
Console.Write("-");
}
Console.Write(b.ToString("X"));
b=table[index].mac5;
if ( b < 0x10)
{
Console.Write("-0");
}
else
{
Console.Write("-");
}
Console.Write(b.ToString("X"));
Console.WriteLine();
}
}
finally
{
// Release the memory.
Marshal.FreeCoTaskMem(buffer);
}
}
}
}
VB.NET Sample Code:
Public Shared Sub GetARPTablr()
' The number of bytes needed.
Dim bytesNeeded As Integer = 0
' The result from the API call.
Dim result As Integer = GetIpNetTable(IntPtr.Zero, bytesNeeded, False)
' Call the function, expecting an insufficient buffer.
If result <> ERROR_INSUFFICIENT_BUFFER Then
' Throw an exception.
Throw New Win32Exception(result)
End If
' Allocate the memory, do it in a try/finally block, to ensure
' that it is released.
Dim buffer As IntPtr = IntPtr.Zero
' Try/finally.
Try
' Allocate the memory.
buffer = Marshal.AllocCoTaskMem(bytesNeeded)
' Make the call again. If it did not succeed, then
' raise an error.
result = GetIpNetTable(buffer, bytesNeeded, False)
' If the result is not 0 (no error), then throw an exception.
If result <> ERROR_SUCCESS Then
' Throw an exception.
Throw New Win32Exception(result)
End If
' Now we have the buffer, we have to marshal it. We can read
' the first 4 bytes to get the length of the buffer.
Dim entries As Integer = Marshal.ReadInt32(buffer)
' Increment the memory pointer by the size of the int.
Dim currentBuffer As New IntPtr(buffer.ToInt64() + Marshal.SizeOf(GetType(Integer)))
' Allocate an array of entries.
Dim table As MIB_IPNETROW() = New MIB_IPNETROW(entries - 1) {}
' Cycle through the entries.
For index As Integer = 0 To entries - 1
' Call PtrToStructure, getting the structure information.
table(index) = DirectCast(Marshal.PtrToStructure(New IntPtr(currentBuffer.ToInt64() + (index * Marshal.SizeOf(GetType(MIB_IPNETROW)))), GetType(MIB_IPNETROW)), MIB_IPNETROW)
Next
For index As Integer = 0 To entries - 1
If table(index).dwType <> DWTYPES.Invalid And table(index).dwType <> DWTYPES.Other Then
Dim ip As New IPAddress(table(index).dwAddr)
Dim mac As New PhysicalAddress(table(index).bPhysAddr)
Console.WriteLine(table(index).dwType.ToString & vbTab & vbTab & "IP:" + ip.ToString() & vbTab & vbTab & "MAC: " & MACtoString(mac))
End If
Next
Finally
' Release the memory.
Marshal.FreeCoTaskMem(buffer)
' Marshal.FreeHGlobal(rowptr)
End Try
End Sub
Public Shared Function MACtoString(mac As PhysicalAddress, Optional Capital As Boolean = True) As String
If Capital Then ' In capital Letters
Return String.Join(":", (From z As Byte In mac.GetAddressBytes Select z.ToString("X2")).ToArray())
Else
Return String.Join(":", (From z As Byte In mac.GetAddressBytes Select z.ToString("x2")).ToArray())
End If
End Function
