[DllImport("iphlpapi.dll", ExactSpelling=true, SetLastError=true)]
private static extern bool GetRTTAndHopCount(uint DestIpAddress, out int HopCount, int MaxHops, out int RTT );

/// <summary>
/// Returns hop count to a host per IP-Address.
/// </summary>
/// <param name="pIpAddresseStr"></param>
/// <returns></returns>
private static int GetHopCount(string pIpAddresseStr) {
	IPAddress lIpAddressEntry;
	byte[] lIpAddressArray;
	uint lIpAddress;

  int lTTL;
  int lHopCount;
  int lErrorCode;

  lIpAddressEntry = IPAddress.Parse(pIpAddresseStr);
  lIpAddressArray = lIpAddressEntry.GetAddressBytes();
  lIpAddress = 0;
  for(int i = 0; i < lIpAddressArray.Length; i++) {
    lIpAddress += (uint)(lIpAddressArray[i] << (8 * i)); 
  }

  if (!GetRTTAndHopCount(lIpAddress, out lHopCount, 60, out lTTL)) {
   lErrorCode = Marshal.GetLastWin32Error();
   throw new Exception("GetRTTAndHopCount has ERROR code = " + lErrorCode);
  }
  return lHopCount;
}