Find net Mask : Net Mask « Network « C# / C Sharp

1. C# / C Sharp
2. Network
3. Net Mask

Find net Mask

/*
C# Network Programming 
by Richard Blum

Publisher: Sybex 
ISBN: 0782141765
*/
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

public class FindMask
{
   public static void Main()
   {
      byte[] data = new byte[1024];
      int recv;
      Socket host = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);
      IPEndPoint iep = new IPEndPoint(IPAddress.Broadcast, 0);
      EndPoint ep = (EndPoint)iep;
      ICMP packet = new ICMP();

      packet.Type = 0x11;
      packet.Code = 0x00;
      packet.Checksum = 0;
      Buffer.BlockCopy(BitConverter.GetBytes(1), 0, packet.Message, 0, 2);
      Buffer.BlockCopy(BitConverter.GetBytes(1), 0, packet.Message, 2, 2);
      Buffer.BlockCopy(BitConverter.GetBytes(0), 0, packet.Message, 4, 4);
      packet.MessageSize = 8;
      int packetsize = packet.MessageSize + 4;

      UInt16 chksm = packet.getChecksum();
      packet.Checksum = chksm;

      host.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 3000);
      host.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, 1);
      host.SendTo(packet.getBytes(), packetsize, SocketFlags.None, iep);
      try
      {
         data = new byte[1024];
         recv = host.ReceiveFrom(data, ref ep);
      } catch (SocketException)
      {
         Console.WriteLine("Unable to determine subnet mask for this subnet");
         return;
      }
      ICMP response = new ICMP(data, recv);
      Console.WriteLine("Received ICMP Type {0} packet", response.Type);
      long answer = BitConverter.ToUInt32(response.Message, 4);
      IPAddress netmask = new IPAddress(answer);
      Console.WriteLine("The subnet mask for this subnet is: {0}", netmask.ToString());
   }
}
class ICMP
{
   public byte Type;
   public byte Code;
   public UInt16 Checksum;
   public int MessageSize;
   public byte[] Message = new byte[1024];

   public ICMP()
   {
   }

   public ICMP(byte[] data, int size)
   {
      Type = data[20];
      Code = data[21];
      Checksum = BitConverter.ToUInt16(data, 22);
      MessageSize = size - 24;
      Buffer.BlockCopy(data, 24, Message, 0, MessageSize);
   }

   public byte[] getBytes()
   {
      byte[] data = new byte[MessageSize + 9];
      Buffer.BlockCopy(BitConverter.GetBytes(Type), 0, data, 0, 1);
      Buffer.BlockCopy(BitConverter.GetBytes(Code), 0, data, 1, 1);
      Buffer.BlockCopy(BitConverter.GetBytes(Checksum), 0, data, 2, 2);
      Buffer.BlockCopy(Message, 0, data, 4, MessageSize);
      return data;
   }

   public UInt16 getChecksum()
   {
      UInt32 chcksm = 0;
      byte[] data = getBytes();
      int packetsize = MessageSize + 8;
      int index = 0;

      while ( index < packetsize)
      {
         chcksm += Convert.ToUInt32(BitConverter.ToUInt16(data, index));
         index += 2;
      }
      chcksm = (chcksm >> 16) + (chcksm & 0xffff);
      chcksm += (chcksm >> 16);
      return (UInt16)(~chcksm);
   }
}
           
       

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