SendARP (iphlpapi)
Last changed: -

Send ARP message to a Network Card in the LAN

C# Signature:

  [DllImport("iphlpapi.dll", ExactSpelling=true)]
  public static extern int SendARP(
      uint DestIP, uint SrcIP, byte[] pMacAddr, ref int PhyAddrLen);

VB Signature:

  Declare Function SendARP Lib "iphlpapi.dll" (
      ByVal DestIP As UInt32, ByVal SrcIP As UInt32, _
      ByVal pMacAddr As Byte(), ByRef PhyAddrLen As Integer) As Integer

User-Defined Types:



SendARP returns 0 on success. The parameter SrcIP can be 0.

Tips & Tricks:

Please add some!

The DestIP and SrcIP arguments should be UInt32 to avoid System.OverflowException when the last nibble of the IP-address is .128 or greater.

Sample Code:

This code help to get the MAC Address of a network card (You need to know the IP address)

Public Shared Function GetMAC(ByVal IPAddress A

    Dim addr As IPAddress = IPAddress.Parse(IPAddress)
    Dim mac() As Byte = New Byte(6) {}
    Dim len As Integer = mac.Length
    SendARP(CType(addr.Address, UInt32), 0, mac, len)
    Dim macAddress As String = BitConverter.ToString(mac, 0, len)
    Return macAddress

End Function

This is a similar C# sample

IPAddress dst = IPAddress.Parse(

// Please do not use the IPAddress.Address property
// This API is now obsolete. -->
// to get the IP in Integer mode use

uint uintAddress = BitConverter.ToUInt32(dst.GetAddressBytes(), 0);
byte[] macAddr = new byte[6];
int macAddrLen = macAddr.Length;
int retValue = SendARP(uintAddress, 0, macAddr, ref macAddrLen);
if (retValue != 0) {
    throw new Win32Exception(retValue, "SendARP failed.");

string[] str = new string[(int)macAddrLen];
for (int i = 0; i < macAddrLen; i++)
    str[i] = macAddr[i].ToString("x2");

Console.WriteLine(string.Join(":", str));

Alternative Managed API:

Do you know one? Please contribute it!