namespace MyPing
{
    using System;
    using System.Net;
    using System.Net.Sockets;
    public class IcmpPacket
    {
        public Byte  Type;    // type of message
        public Byte  SubCode;    // type of sub code
        public UInt16 CheckSum;   // ones complement checksum of struct
        public UInt16 Identifier;      // identifier
        public UInt16 SequenceNumber;     // sequence number
        public Byte [] Data;
    } // class IcmpPacket
    class Ping
    {
        const int SOCKET_ERROR = -1;
        const int ICMP_ECHO = 8;
        public static void Main(string[] argv)
        {
            if(argv.Length==0)
            {
                Console.WriteLine("Usage:Ping <hostname> -t") ;
                Console.WriteLine("<hostname> The name of the Host who you want to ping");
                Console.WriteLine("-t Optional Switch to Ping the host continuously") ;
            }
            else if(argv.Length==1)
            {
                PingHost(argv[0]) ;
            }
            else if(argv.Length==2)
            {
                if(argv[1]=="-t")
                {
                    while(true)
                    {
                        PingHost(argv[0]) ;
                    }
                }
                else
                {
                    PingHost(argv[0]) ;
                }
            }
            else
            {
                Console.WriteLine("Error in Arguments") ;
            }
        }
        public static void PingHost(string host)
        {
            IPHostEntry serverHE, fromHE;
            int nBytes = 0;
            int dwStart = 0, dwStop = 0;
            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);
            try
            {
                serverHE = Dns.GetHostByName(host);
            }
            catch(Exception)
            {
                Console.WriteLine("Host not found"); // fail
                return ;
            }
            IPEndPoint ipepServer = new IPEndPoint(serverHE.AddressList[0], 0);
            EndPoint epServer = (ipepServer);
            fromHE = Dns.GetHostByName(Dns.GetHostName());
            IPEndPoint ipEndPointFrom = new IPEndPoint(fromHE.AddressList[0], 0);
            EndPoint EndPointFrom = (ipEndPointFrom);
            int PacketSize = 0;
            IcmpPacket packet = new IcmpPacket();
            packet.Type = ICMP_ECHO; //8
            packet.SubCode = 0;
            packet.CheckSum = UInt16.Parse("0");
            packet.Identifier   = UInt16.Parse("45");
            packet.SequenceNumber  = UInt16.Parse("0");
            int PingData = 32; // sizeof(IcmpPacket) - 8;
            packet.Data = new Byte[PingData];
            for (int i = 0; i < PingData; i++)
                packet.Data[i] = (byte)'#';
            PacketSize = PingData + 8;
            Byte [] icmp_pkt_buffer = new Byte[ PacketSize ];
            Int32 Index = 0;
            Index = Serialize(packet,icmp_pkt_buffer,PacketSize,PingData);
            if( Index == -1 )
            {
                Console.WriteLine("Error in Making Packet");
                return ;
            }
            Double double_length = Convert.ToDouble(Index);
            Double dtemp = Math.Ceiling( double_length / 2);
            int cksum_buffer_length = Convert.ToInt32(dtemp);
            UInt16 [] cksum_buffer = new UInt16[cksum_buffer_length];
            int icmp_header_buffer_index = 0;
            for( int i = 0; i < cksum_buffer_length; i++ ) 
            {
                cksum_buffer[i] =
                    BitConverter.ToUInt16(icmp_pkt_buffer,icmp_header_buffer_index);
                icmp_header_buffer_index += 2;
            }
            UInt16 u_cksum = checksum(cksum_buffer, cksum_buffer_length);
            packet.CheckSum  = u_cksum;
            Byte [] sendbuf = new Byte[ PacketSize ];
            Index = Serialize(packet,sendbuf,PacketSize,PingData);
            if( Index == -1 )
            {
                Console.WriteLine("Error in Making Packet");
                return ;
            }
            dwStart = System.Environment.TickCount; // Start timing
            if ((nBytes = socket.SendTo(sendbuf, PacketSize, 0, epServer)) == SOCKET_ERROR)
            {
                Console.WriteLine("Socket Error cannot Send Packet");
            }
            Byte [] ReceiveBuffer = new Byte[256];
            nBytes = 0;
            bool recd =false ;
            int timeout=0 ;
            while(!recd)
            {
                nBytes = socket.ReceiveFrom(ReceiveBuffer, 256, 0, ref EndPointFrom);
                if (nBytes == SOCKET_ERROR)
                {
                    Console.WriteLine("Host not Responding") ;
                    recd=true ;
                    break;
                }
                else if(nBytes>0)
                {
                    dwStop = System.Environment.TickCount - dwStart; // stop timing
                    Console.WriteLine("Reply from "+epServer.ToString()+" in "+dwStop+"MS,\tBytes Received :"+nBytes);
                    recd=true;
                    break;
                }
                timeout=System.Environment.TickCount - dwStart;
                if(timeout>1000)
                {
                    Console.WriteLine("Time Out") ;
                    recd=true;
                }
            }
            socket.Close();
        }
        public static Int32 Serialize(  IcmpPacket packet, Byte [] Buffer, Int32 PacketSize, Int32 PingData )
        {
            Int32 cbReturn = 0;
            int Index=0;
            Byte [] b_type = new Byte[1];
            b_type[0] = (packet.Type);
            Byte [] b_code = new Byte[1];
            b_code[0] = (packet.SubCode);
            Byte [] b_cksum = BitConverter.GetBytes(packet.CheckSum);
            Byte [] b_id = BitConverter.GetBytes(packet.Identifier);
            Byte [] b_seq = BitConverter.GetBytes(packet.SequenceNumber);
            Array.Copy( b_type, 0, Buffer, Index, b_type.Length );
            Index += b_type.Length;
            Array.Copy( b_code, 0, Buffer, Index, b_code.Length );
            Index += b_code.Length;
            Array.Copy( b_cksum, 0, Buffer, Index, b_cksum.Length );
            Index += b_cksum.Length;
            Array.Copy( b_id, 0, Buffer, Index, b_id.Length );
            Index += b_id.Length;
            Array.Copy( b_seq, 0, Buffer, Index, b_seq.Length );
            Index += b_seq.Length;
            Array.Copy( packet.Data, 0, Buffer, Index, PingData );
            Index += PingData;
            if( Index != PacketSize )
            {
                cbReturn = -1;
                return cbReturn;
            }
            cbReturn = Index;
            return cbReturn;
        }
        public static UInt16 checksum( UInt16[] buffer, int size )
        {
            Int32 cksum = 0;
            int counter;
            counter = 0;
            while ( size > 0 )
            {
                UInt16 val = buffer[counter];
                cksum += Convert.ToInt32( buffer[counter] );
                counter += 1;
                size -= 1;
            }
            cksum = (cksum >> 16) + (cksum & 0xffff);
            cksum += (cksum >> 16);
            return (UInt16)(~cksum);
        }
    } // class ping
}