exp 2  

import java.io.*;
import java.net.URL;

public class downlaod{
    public static void main(String[] args) throws Exception
    {

    try{
        String filename="sample.html";
        String website="https://ssmiet.ac.in/";
        URL url=new URL(website);
        System.out.println("the web file is downloading "+ website);
        InputStream inputStream=url.openStream();
        OutputStream outputStream= new FileOutputStream(filename);
        byte[] buffer=new byte[2048];
        int length=0;
        while ((length=inputStream.read(buffer)) != -1){
            System.out.println("The buffer lenght" + length);
            outputStream.write(buffer,0, length);
        }
        inputStream.close();
        outputStream.close();
    } 
    catch( Exception e){
        System.out.println("Exception" + e.getMessage());
    }
    }
}

Ex 3a client.java 

import java.io.DataInputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.net.InetAddress;
import java.net.Socket;

public class Client {

    public static void main(String[] args) {

        Socket sock = null;

        try {
            System.out.println("Trying to connect...");

            
            sock = new Socket(InetAddress.getLocalHost(), Server.PORT);

            
            PrintStream ps = new PrintStream(sock.getOutputStream());
            ps.println("Hi from client");

            
            DataInputStream dis = new DataInputStream(sock.getInputStream());
            System.out.println("Server says: " + dis.readLine());

            ps.close();
            dis.close();

        } catch (IOException e) {
            System.out.println("Connection Error: " + e.getMessage());
        } finally {
            try {
                if (sock != null)
                    sock.close();
            } catch (IOException ie) {
                System.out.println("Close Error: " + ie.getMessage());
            }
        }
    }
}

server.java

import java.io.DataInputStream;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {

    public static final int PORT = 4000;

    public static void main(String[] args) {

        ServerSocket sersock = null;
        Socket sock = null;

        try {
            sersock = new ServerSocket(PORT);
            System.out.println("Server started on: " + sersock);

            sock = sersock.accept();
            System.out.println("Client connected: " + sock);

            DataInputStream ins = new DataInputStream(sock.getInputStream());
            String msg = ins.readLine();
            System.out.println("Client says: " + msg);

            PrintStream ios = new PrintStream(sock.getOutputStream());
            ios.println("Hello from server");

            ios.close();
            sock.close();
            sersock.close();

        } catch (Exception e) {
            System.out.println("Server error: " + e.getMessage());
        }
    }
}

EX3b  chatserver

import java.io.*;
import java.net.*;

class TopChatServer {

    public static void main(String args[]) throws Exception {

        PrintWriter toclient;
        BufferedReader fromuser, fromclient;

        try {
            ServerSocket srv = new ServerSocket(4000);
            System.out.println("Server started");

            Socket clt = srv.accept();
            System.out.println("Client connected");

            toclient = new PrintWriter(
                        new BufferedWriter(
                            new OutputStreamWriter(clt.getOutputStream())), true);

            fromclient = new BufferedReader(
                            new InputStreamReader(clt.getInputStream()));

            fromuser = new BufferedReader(
                            new InputStreamReader(System.in));

            String cltmsg, srvmsg;

            while (true) {
                cltmsg = fromclient.readLine();

                if (cltmsg == null || cltmsg.equalsIgnoreCase("end"))
                    break;

                System.out.println("Client: " + cltmsg);

                System.out.print("Server: ");
                srvmsg = fromuser.readLine();

                toclient.println(srvmsg);
            }

            System.out.println("Client Disconnected");

            fromclient.close();
            toclient.close();
            fromuser.close();
            clt.close();
            srv.close();

        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

chatclient

import java.io.*;
import java.net.*;

class TpcChatClient {

    public static void main(String args[]) throws Exception {

        Socket clt;
        PrintWriter toserver;

        try {
            BufferedReader fromuser, fromserver;

            clt = new Socket(InetAddress.getLocalHost(), 4000);

            toserver = new PrintWriter(
                        new BufferedWriter(
                            new OutputStreamWriter(clt.getOutputStream())), true);

            fromserver = new BufferedReader(
                            new InputStreamReader(clt.getInputStream()));

            fromuser = new BufferedReader(
                            new InputStreamReader(System.in));

            String cltmsg, srvmsg;

            System.out.println("Type \"end\" to quit");

            while (true) {

                System.out.print("Message to server: ");
                cltmsg = fromuser.readLine();

                if (cltmsg.equalsIgnoreCase("end"))
                    break;

                toserver.println(cltmsg);

                srvmsg = fromserver.readLine();
                System.out.println("Server: " + srvmsg);
            }

            clt.close();
            toserver.close();
            fromserver.close();
            fromuser.close();

        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

Ex 6a

dnsserver.java 

import java.net.*;

public class DNSServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket ds = new DatagramSocket(5000);
        byte[] recv = new byte[1024];
        byte[] send;

        System.out.println("DNS Server running...");

        while (true) {
            DatagramPacket dp = new DatagramPacket(recv, recv.length);
            ds.receive(dp);
            String domain = new String(dp.getData(), 0, dp.getLength());

            String ip;
            if (domain.equals("google.com"))
                ip = "8.8.8.8";
            else if (domain.equals("yahoo.com"))
                ip = "98.137.11.164";
            else
                ip = "Domain Not Found";

            send = ip.getBytes();
            DatagramPacket sp = new DatagramPacket(send, send.length, dp.getAddress(), dp.getPort());
            ds.send(sp);
        }
    }
}

dnsclient .java 

import java.net.*;
import java.io.*;

public class DNSClient {
    public static void main(String[] args) throws Exception {
        DatagramSocket ds = new DatagramSocket();
        InetAddress ip = InetAddress.getByName("127.0.0.1");

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter domain: ");
        String domain = br.readLine();

        byte[] send = domain.getBytes();
        byte[] recv = new byte[1024];

        DatagramPacket sp = new DatagramPacket(send, send.length, ip, 5000);
        ds.send(sp);

        DatagramPacket rp = new DatagramPacket(recv, recv.length);
        ds.receive(rp);

        String result = new String(rp.getData(), 0, rp.getLength());
        System.out.println("IP Address: " + result);

        ds.close();
    }
}


ex 6a

arpserver.java

import java.net.*;
import java.io.*;
import java.util.*;

public class ArpServer {
    public static void main(String[] args) throws Exception {
        HashMap<String, String> arpTable = new HashMap<>();
        arpTable.put("192.168.1.1", "00-A0-C9-14-C8-29");
        arpTable.put("192.168.1.2", "00-A0-C9-14-C8-30");
        arpTable.put("192.168.1.3", "00-A0-C9-14-C8-31");

        ServerSocket ss = new ServerSocket(5000);
        System.out.println("ARP Server Running...");

        Socket s = ss.accept();
        BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
        PrintWriter out = new PrintWriter(s.getOutputStream(), true);

        String ip = in.readLine();

        String mac;
        if (arpTable.containsKey(ip))
            mac = arpTable.get(ip);
        else
            mac = "MAC Address Not Found";

        out.println(mac);

        s.close();
        ss.close();
    }
}

arpclient.java

import java.net.*;
import java.io.*;

public class ArpClient {
    public static void main(String[] args) throws Exception {
        Socket s = new Socket("127.0.0.1", 5000);

        BufferedReader user = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(s.getOutputStream(), true);
        BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));

        System.out.print("Enter IP Address: ");
        String ip = user.readLine();

        out.println(ip);

        String mac = in.readLine();
        System.out.println("MAC Address: " + mac);

        s.close();
    }
}

ex 6b

rarpserver.java

import java.net.*;
import java.io.*;
import java.util.*;

public class RarpServer {
    public static void main(String[] args) throws Exception {
        HashMap<String, String> rarpTable = new HashMap<>();
        rarpTable.put("00-A0-C9-14-C8-29", "192.168.1.1");
        rarpTable.put("00-A0-C9-14-C8-30", "192.168.1.2");
        rarpTable.put("00-A0-C9-14-C8-31", "192.168.1.3");

        ServerSocket ss = new ServerSocket(6000);
        System.out.println("RARP Server Running...");

        Socket s = ss.accept();
        BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
        PrintWriter out = new PrintWriter(s.getOutputStream(), true);

        String mac = in.readLine();

        String ip;
        if (rarpTable.containsKey(mac))
            ip = rarpTable.get(mac);
        else
            ip = "IP Address Not Found";

        out.println(ip);

        s.close();
        ss.close();
    }
}

rarpclient.java

import java.net.*;
import java.io.*;

public class RarpClient {
    public static void main(String[] args) throws Exception {
        Socket s = new Socket("127.0.0.1", 6000);

        BufferedReader user = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(s.getOutputStream(), true);
        BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));

        System.out.print("Enter MAC Address: ");
        String mac = user.readLine();

        out.println(mac);

        String ip = in.readLine();
        System.out.println("IP Address: " + ip);

        s.close();
    }
}

ex 9

disattn vector.java

import java.util.*;

public class DistanceVector {
    public static void main(String[] args) {
        int INF = 999;
        int n = 4;

        int cost[][] = {
            {0, 1, 3, INF},
            {1, 0, 1, 4},
            {3, 1, 0, 2},
            {INF, 4, 2, 0}
        };

        int dist[][] = new int[n][n];
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++)
                dist[i][j] = cost[i][j];

        boolean changed = true;
        while (changed) {
            changed = false;
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < n; j++) {
                    for (int k = 0; k < n; k++) {
                        if (dist[i][j] > cost[i][k] + dist[k][j]) {
                            dist[i][j] = cost[i][k] + dist[k][j];
                            changed = true;
                        }
                    }
                }
            }
        }

        System.out.println("Distance Vector Routing Table");
        for (int i = 0; i < n; i++) {
            System.out.print("Node " + i + ": ");
            for (int j = 0; j < n; j++)
                System.out.print(dist[i][j] + " ");
            System.out.println();
        }
    }
}

linel.java

import java.util.*;

public class LinkState {
    public static void main(String[] args) {
        int INF = 999;
        int n = 5;

        int graph[][] = {
            {0, 2, INF, 1, INF},
            {2, 0, 3, 2, INF},
            {INF, 3, 0, 4, 5},
            {1, 2, 4, 0, 3},
            {INF, INF, 5, 3, 0}
        };

        int src = 0;
        int dist[] = new int[n];
        boolean vis[] = new boolean[n];

        for (int i = 0; i < n; i++)
            dist[i] = graph[src][i];

        vis[src] = true;
        dist[src] = 0;

        for (int c = 1; c < n; c++) {
            int u = -1, min = INF;
            for (int i = 0; i < n; i++)
                if (!vis[i] && dist[i] < min) {
                    min = dist[i];
                    u = i;
                }

            vis[u] = true;

            for (int v = 0; v < n; v++)
                if (!vis[v] && graph[u][v] + dist[u] < dist[v])
                    dist[v] = graph[u][v] + dist[u];
        }

        System.out.println("Link State Routing Table (Source = 0)");
        for (int i = 0; i < n; i++)
            System.out.println("Distance to " + i + " = " + dist[i]);
    }
}
exp 10

import java.util.*;

public class SimpleCRC {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter Data Bits: ");
        String data = sc.nextLine();

        System.out.print("Enter Divisor: ");
        String divisor = sc.nextLine();

        int n = divisor.length() - 1;

        String appended = data + "0".repeat(n);

        String remainder = getRemainder(appended, divisor);

        String codeword = data + remainder;

        System.out.println("Remainder: " + remainder);
        System.out.println("Transmitted Codeword: " + codeword);

        System.out.print("Enter Received Codeword: ");
        String recv = sc.nextLine();

        String check = getRemainder(recv, divisor);

        if (check.equals("0".repeat(n)))
            System.out.println("No Error Detected");
        else
            System.out.println("Error Detected");
    }

    public static String getRemainder(String dividend, String divisor) {
        int m = divisor.length();
        String temp = dividend.substring(0, m);

        for (int i = m; i < dividend.length(); i++) {
            if (temp.charAt(0) == '1')
                temp = xor(temp, divisor) + dividend.charAt(i);
            else
                temp = xor(temp, "0".repeat(m)) + dividend.charAt(i);
        }

        if (temp.charAt(0) == '1')
            temp = xor(temp, divisor);
        else
            temp = xor(temp, "0".repeat(m));

        return temp.substring(1);
    }

    public static String xor(String a, String b) {
        String result = "";
        for (int i = 0; i < a.length(); i++) {
            result += (a.charAt(i) == b.charAt(i)) ? '0' : '1';
        }
        return result;
    }
}