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using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

public class SimplePing
{
    public static void Main(string[] argv)
    {

        int port;
        string ip;
        byte[] data = new byte[1024];
        int receive;
        Start:
        Console.WriteLine("\n");
        Console.WriteLine("Benutzereigaben");
        Console.WriteLine("═══════════════════════════");
        Console.Write("Empfänger IP:");
        ip = Convert.ToString(Console.ReadLine());
        Console.Write("Auf welchen Port:");
        port = Convert.ToInt16(Console.ReadLine());


        Socket host = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);

        IPEndPoint iep = new IPEndPoint(IPAddress.Parse(ip), port);
        EndPoint ep = (EndPoint)iep;

        

            data = Encoding.ASCII.GetBytes("11111111111111");

            ICMP packet = new ICMP();
            packet.Code = 0x00;
            packet.Type = 0x00;
            packet.Message = data;
            packet.MessageSize = data.Length;
            int packetsize = packet.MessageSize + 4;
            UInt16 chcksum = packet.getChecksum();
            packet.Checksum = chcksum;

            host.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 10000);
            host.SendTo(packet.getBytes(), packetsize, SocketFlags.None, ep);

            data = new byte[1024];
            receive = host.ReceiveFrom(data, ref ep);

            ICMP response = new ICMP(data, receive);

            Console.WriteLine("\n");
            Console.WriteLine("Antwort von: {0}", ep.ToString());
            Console.WriteLine("  Type {0}", response.Type);
            Console.WriteLine("  Code: {0}", response.Code);
            int Identifier = BitConverter.ToInt16(response.Message, 0);
            int Sequence = BitConverter.ToInt16(response.Message, 2);
            Console.WriteLine("  Identifier: {0}", Identifier);
            Console.WriteLine("  Sequence: {0}", Sequence);
            Console.WriteLine("  CheckSum: {0}",chcksum);
            goto Start;

            host.Close();


        Console.ReadKey();

        
    }
}

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);
    }
}