IP Server

//Server Code
//Distributed Systems (Client/Server Project)
//By Mohammad Mahjoub and Zahi Ismail
//Presented to Dr. Ramzi Haraty
//23/4/2007

//About Project: 
//The client issues a request to get status of range of IP addresses
//The server fetches the request and checks the status by issuing successive ping commands
//to each IP address in the range, it then returns the results to the client to be displayed 
//to the user.The server can serve many clients concurrently.
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;


public class Server {

    public static String myAddress;//address range received from the client
    public static String myMessage;//message containing the results to be returned to the client
    public static Ping ping = new Ping();//Create a new Ping instance using Ping class
   
	public static void Main() {

            
      try {
        
 		IPAddress ipAddress = IPAddress.Parse("127.0.0.1"); //Using localhost address
        TcpListener theList = new TcpListener(ipAddress, 2000); //Initializes the listener to localhost address and port 2000
        
        Console.WriteLine("\nServer started");
        Console.WriteLine("The server is running at 127.0.0.1:2000...");
        Console.WriteLine("Waiting for an incoming connection.....");
          
        
        
        while (true)
        {
            theList.Start(); //Start listening
            Socket s = theList.AcceptSocket();//accept the client connection
            Console.WriteLine("\nConnection accepted from host " + s.RemoteEndPoint);
            Console.WriteLine("\nWaiting for IP range");

                byte[] b = new byte[100];//buffer to store incoming characters stream
                int k = s.Receive(b);//k is the number of characters received


                for (int i = 0; i < k; i++)
                {
                    myAddress = myAddress + (Convert.ToChar(b[i]).ToString());//Convert received characters stream into string
                }                                                             //store the incoming range in myAddress variable

                Console.WriteLine("\nIP range:");
                string[] addressRange = myAddress.Split(new Char[] { '|' });//Split based on the character |
                Console.WriteLine("From:" + addressRange[0] + " To:" + addressRange[1]);

                string[] fromAddress = addressRange[0].Split(new Char[] { '.' });//Split the lower bound IP address into four octets
                string[] toAddress = addressRange[1].Split(new Char[] { '.' });//Split the upper bound IP address into four octets

                String fromFirst = fromAddress[0];//Lower bound first octet
                String fromSecond = fromAddress[1];//Lower bound second octet
                String fromThird = fromAddress[2];//Lower bound third octet
                String fromFourth = fromAddress[3];//Lower bound fourth octet
                String toFourth = toAddress[3];//Upper bound last octet


                //The below routine does the ping for each IP address in the range
                for (int x = int.Parse(fromFourth); x <= int.Parse(toFourth); x++)
                {
                    ping.Open();
                    TimeSpan span = ping.Send(fromFirst.ToString() + "." + fromSecond.ToString() + "." + fromThird.ToString() + "." + x.ToString(), new TimeSpan(0, 0, 5));
                    ping.Close();

                    //Appending the result of each ping to myMessage string to be send to the host
                    if (span == TimeSpan.MaxValue)

                        myMessage = myMessage + (fromFirst.ToString() + "." + fromSecond.ToString() + "." + fromThird.ToString() + "." + x.ToString() + "     Offline\n");

                    else
                    {
                        myMessage = myMessage + (fromFirst.ToString() + "." + fromSecond.ToString() + "." + fromThird.ToString() + "." + x.ToString() + "     Online\n");

                    }
                }//end of for loop


                ASCIIEncoding asen = new ASCIIEncoding();//Sending ping results to the host using ASCII encoding
                s.Send(asen.GetBytes(myMessage));

                Console.WriteLine("\nIP range processed by the server");
                Console.WriteLine("\nIP status results sent to client");
                myAddress = "";//Resetting myAddress string
                myMessage = "";//Resetting myMessage string
                s.Close();          
            }//End of while loop

           
                  
	}//End of try block
	catch (Exception ex) {
		
        Console.WriteLine("Host disconnected");
                
	}	
	}

}

#region Ping

public class Ping
{
    /*_______________________________________________________________*/
    // methods: Construction
    #region

    // Constructor
    public Ping()
    {
        // create command field
        pingCommand = new byte[8];
        pingCommand[0] = 8;			// Type
        pingCommand[1] = 0;			// Subtype
        pingCommand[2] = 0;			// Checksum
        pingCommand[3] = 0;
        pingCommand[4] = 1;			// Identifier
        pingCommand[5] = 0;
        pingCommand[6] = 0;			// Sequence number
        pingCommand[7] = 0;

        // create result field
        pingResult = new byte[pingCommand.Length + 1000];	// returned IP Header + optional data
    }
    #endregion


    /*_______________________________________________________________*/
    // methods: Open, Close, Send
    #region

    // Open
    public void Open()
    {
        // create socket and connect
        socket = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp);
        isOpen = true;

        // create read complete event
        readComplete = new ManualResetEvent(false);
    }

    // Close
    public void Close()
    {
        // clear open flag
        isOpen = false;

        // close socket
        socket.Close();

        // close event
        readComplete.Close();
    }

    // Send
    public TimeSpan Send(string address, TimeSpan timeout) // This method returns TimsSpan
    {
        // empty result buffer
        while (socket.Available > 0)
            socket.Receive(pingResult, Math.Min(socket.Available, pingResult.Length), SocketFlags.None);

        // reset event
        readComplete.Reset();

        // save start time
        DateTime timeSend = DateTime.Now;

        // complete ping command
        pingCommand[6] = lastSequenceNr++;
        SetChecksum(pingCommand);

        // send ping command, start receive command

        try
        {

            int iSend = socket.SendTo(pingCommand, new IPEndPoint(IPAddress.Parse(address), 0));
            socket.BeginReceive(pingResult, 0, pingResult.Length, SocketFlags.None, new AsyncCallback(CallBack), null);

            // wait until data received or timeout
            if (readComplete.WaitOne(timeout, false))
            {
                // check result
                if ((pingResult[20] == 0) &&
                    (pingCommand[4] == pingResult[24]) && (pingCommand[5] == pingResult[25]) &&
                    (pingCommand[6] == pingResult[26]) && (pingCommand[7] == pingResult[27]))
                    // return time delay
                    return DateTime.Now.Subtract(timeSend);
            }

            // return timeout
            return TimeSpan.MaxValue;
        }
        catch (Exception ex)
        {
            return TimeSpan.MaxValue;
        }


    }
    #endregion


    /*_______________________________________________________________*/
    // methods: CallBack
    #region

    protected void CallBack(IAsyncResult result)
    {
        if (isOpen)
        {
            try { socket.EndReceive(result); }
            catch (Exception) { }
            readComplete.Set();
        }
    }
    #endregion


    /*_______________________________________________________________*/
    // methods: SetChecksum
    #region

    protected void SetChecksum(byte[] tel)
    {
        // reset old checksum
        tel[2] = 0;
        tel[3] = 0;

        // calculate new checksum
        uint cs = 0;
        for (int i = 0; i < pingCommand.Length; i = i + 2)
            cs += BitConverter.ToUInt16(pingCommand, i);
        cs = ~((cs & 0xffffu) + (cs >> 16));

        // set new checksum
        tel[2] = (byte)cs;
        tel[3] = (byte)(cs >> 8);
    }
    #endregion



    /*...............................................................*/
    // fields

    // socket and event
    protected Socket socket;
    protected bool isOpen;
    protected ManualResetEvent readComplete;
    protected byte lastSequenceNr = 0;

    // ping command and result fields
    protected byte[] pingCommand;
    protected byte[] pingResult;
}
#endregion