NETWORK

ques 1 : Server's date and time at client side

client:
import java.io.*;
import java.net.*;
import java.util.*;
class DateClient
{
	public static void main(String[] arga) throws Exception
	{
		Socket cs = new Socket("localhost",9999);
		DataInputStream in = new DataInputStream(cs.getInputStream());
		System.out.println(in.readLine());
		in.close();
	}
}

Server:

import java.io.*;
import java.net.*;
import java.util.*;
class DateServer
{
	public static void main(String[] arga) throws Exception
	{
		ServerSocket ss = new ServerSocket(9999);
		String line;
		Socket cs = ss.accept();
		DataInputStream in = new DataInputStream(cs.getInputStream());
		PrintStream os = new PrintStream(cs.getOutputStream());
		os.println("Server Date" + (new Date()).toString() + "\n");
		in.close();
		os.close();
	}
}

Ques 2: Client address at server
Client::
import java.io.*;
import java.net.*;
import java.util.*;
class ClientSecond
{
	public static void main(String[] arga) throws Exception
	{
		Socket cs = new Socket("localhost",9999);
		DataInputStream in = new DataInputStream(cs.getInputStream());
		System.out.println(in.readLine());
		in.close();
	}
}
Server::
import java.io.*;
import java.net.*;
import java.util.*;
class ServerSecond
{
	public static void main(String[] arga) throws Exception
	{
		ServerSocket ss = new ServerSocket(9999);
		String line;
		Socket cs = ss.accept();
		DataInputStream in = new DataInputStream(cs.getInputStream());
		PrintStream os = new PrintStream(cs.getOutputStream());
		os.println("Server Date" + (new Date()).toString() + "\n");
		InetAddress addr = ss.getInetAddress();

		System.out.println(addr);


		in.close();
		os.close();
	}
}

Ques 3:Echo UDP Server
Cient::
import java.io.*;
import java.net.*;

public class ClientThree
{
    public static void main(String args[])
    {
        DatagramSocket sock = null;
        int port = 7777;
        String s;

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

        try
        {
            sock = new DatagramSocket();

            InetAddress host = InetAddress.getByName("localhost");

            while(true)
            {
                //take input and send the packet
                echo("Enter message to send : ");
                s = (String)cin.readLine();
                byte[] b = s.getBytes();

                DatagramPacket  dp = new DatagramPacket(b , b.length , host , port);
                sock.send(dp);

                //now receive reply
                //buffer to receive incoming data
                byte[] buffer = new byte[65536];
                DatagramPacket reply = new DatagramPacket(buffer, buffer.length);
                sock.receive(reply);

                byte[] data = reply.getData();
                s = new String(data, 0, reply.getLength());

                //echo the details of incoming data - client ip : client port - client message
                echo(reply.getAddress().getHostAddress() + " : " + reply.getPort() + " - " + s);
            }
        }

        catch(IOException e)
        {
            System.err.println("IOException " + e);
        }
    }

    //simple function to echo data to terminal
    public static void echo(String msg)
    {
        System.out.println(msg);
    }
}

Server::

import java.io.*;
import java.net.*;
import java.util.*;
class ServerThree
{
	public static void main(String[] args) throws Exception
	{
		DatagramSocket ds = new DatagramSocket(7777);
		byte[] buffer = new byte[65536];
		DatagramPacket packet = new DatagramPacket(buffer,buffer.length);
		while(true)
		{
			ds.receive(packet);
			byte[] data = packet.getData();
			String s = new String(data, 0, packet.getLength());
			echo(packet.getAddress().getHostAddress() + " : " + packet.getPort() + " - " + s);

                s = "OK : " + s;
                DatagramPacket dp = new DatagramPacket(s.getBytes() , s.getBytes().length , packet.getAddress() , packet.getPort());
                ds.send(dp);
		}
	}
	public static void echo(String msg)
    {
        System.out.println(msg);
    }
}

ques4:: simple chat app

client ::
import java.io.*;
import java.net.*;
import java.util.*;
class ClientFour
{
	public static void main(String[] arga) throws Exception
	{
		Socket cs = new Socket("localhost",8888);
		DataInputStream in = new DataInputStream(cs.getInputStream());
		PrintStream out = new PrintStream(cs.getOutputStream());
		BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
		String s;
		while (  true )
		{
			System.out.print("Client : ");
			s=stdin.readLine();
			out.println(s);
			s=in.readLine();
			System.out.print("Server : "+s+"\n");
  			if ( s.equalsIgnoreCase("BYE") )
 			   break;
		}
		out.close();
		in.close();
		cs.close();
		stdin.close();
	}
}
Server::
import java.io.*;
import java.net.*;
import java.util.*;
class ServerFour
{
	public static void main(String[] arga) throws Exception
	{
		ServerSocket ss = new ServerSocket(8888);
		Socket cs = ss.accept();
		DataInputStream in = new DataInputStream(cs.getInputStream());
		PrintStream out = new PrintStream(cs.getOutputStream());
		BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
		String s;
		while (  true )
		{
			s=in.readLine();
  			if (s.equalsIgnoreCase("END"))
  			{
				out.println("BYE");
    				break;
  			  }
			System. out.print("Client : "+s+"\n");
			System.out.print("Server : ");
			s=stdin.readLine();
			out.println(s);
		}



		cs.close();
		ss.close();
		in.close();
		out.close();
	}
}



4. Write a Java program to develop a simple Chat application.

Server

import java.io.*;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.*;
public class GossipServer
{
  public static void main(String[] args) throws Exception
  {
      ServerSocket sersock = new ServerSocket(3000);
      Socket sock = sersock.accept( );
                              // reading from keyboard (keyRead object)
      BufferedReader keyRead = new BufferedReader(new InputStreamReader(System.in));
                      // sending to client (pwrite object)
      OutputStream ostream = sock.getOutputStream();
      PrintWriter pwrite = new PrintWriter(ostream, true);

                              // receiving from server ( receiveRead  object)
      InputStream istream = sock.getInputStream();
      BufferedReader receiveRead = new BufferedReader(new InputStreamReader(istream));

      String receiveMessage, sendMessage;
      while(true)
      {
        if((receiveMessage = receiveRead.readLine()) != null)
        {
           System.out.println(receiveMessage);
        }
        sendMessage = keyRead.readLine();
        pwrite.println(sendMessage);
        pwrite.flush();
      }
    }
}

Client
import java.io.*;
import java.net.*;
public class GossipClient
{
  public static void main(String[] args) throws Exception
  {
     Socket sock = new Socket("127.0.0.1", 3000);
                               // reading from keyboard (keyRead object)
     BufferedReader keyRead = new BufferedReader(new InputStreamReader(System.in));
                              // sending to client (pwrite object)
     OutputStream ostream = sock.getOutputStream();
     PrintWriter pwrite = new PrintWriter(ostream, true);

                              // receiving from server ( receiveRead  object)
     InputStream istream = sock.getInputStream();
     BufferedReader receiveRead = new BufferedReader(new InputStreamReader(istream));

     System.out.println("Start the chitchat, type and press Enter key");

     String receiveMessage, sendMessage;
     while(true)
     {
        sendMessage = keyRead.readLine();  // keyboard reading
        pwrite.println(sendMessage);       // sending to server
        pwrite.flush();                    // flush the data
        if((receiveMessage = receiveRead.readLine()) != null) //receive from server
        {
            System.out.println(receiveMessage); // displaying at DOS prompt
        }
      }
    }
}



5. The message entered in the client is sent to the server and the server encodes the message and
returns it to the client. Encoding is done by replacing a character by the character next to it i.e. a as b,
b as c …z as a. This process is done using the TCP/IP protocol. Write a Java program for the above


client
import java.io.*;
import java.net.*;
import java.util.*;
class ClientFive
{
	public static void main(String[] arga) throws Exception
	{
		Socket cs = new Socket("localhost",8888);
		DataInputStream in = new DataInputStream(cs.getInputStream());
		PrintStream out = new PrintStream(cs.getOutputStream());
		BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
		String s;
		while (  true )
		{
			System.out.print("Client : ");
			s=stdin.readLine();
			out.println(s);
			s=in.readLine();
			System.out.print("Server : "+s+"\n");
  			if ( s.equalsIgnoreCase("BYE") )
 			   break;
		}
		out.close();
		in.close();
		cs.close();
		stdin.close();
	}
}

Server



import java.io.*;
import java.net.*;
import java.util.*;
class ServerFive
{
	public static void main(String[] arga) throws Exception
	{
		ServerSocket ss = new ServerSocket(8888);
		Socket cs = ss.accept();
		DataInputStream in = new DataInputStream(cs.getInputStream());
		PrintStream out = new PrintStream(cs.getOutputStream());
		BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in));
		String s;
		while (  true )
		{
			s=in.readLine();
  			if (s.equalsIgnoreCase("END"))
  			{
				out.println("BYE");
    				break;
  			  }

			String s1="";
			for(char c : s.toCharArray())
			{
				int x = (int)c;

				if(x>=65 && x<=90)
				{
				x=(((x+1)-65)%26)+65;
				s1 += Character.toString((char)x);
				}
				else if(x>=97 && x<=122)
				{
				x=(((x+1)-97)%26)+97;
				s1 += Character.toString((char)x);
				}
				else
				{
				s1 += c;
				}

			}

			System. out.print("Client : "+s+"\n");


			out.println(s1);
		}



		cs.close();
		ss.close();
		in.close();
		out.close();
	}
}
6. The message entered in the client is sent to the server and the server encodes the message and
returns it to the client. Encoding is done by replacing a character by the character next to it i.e. a as b,
b as c …z as a. This process is done using UDP. Write a Java program for the above

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

public class ClientSix
{
    public static void main(String args[])
    {
        DatagramSocket sock = null;
        int port = 7777;
        String s;

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

        try
        {
            sock = new DatagramSocket();

            InetAddress host = InetAddress.getByName("localhost");

            while(true)
            {
                //take input and send the packet
                echo("Enter message to send : ");
                s = (String)cin.readLine();
                byte[] b = s.getBytes();

                DatagramPacket  dp = new DatagramPacket(b , b.length , host , port);
                sock.send(dp);

                //now receive reply
                //buffer to receive incoming data
                byte[] buffer = new byte[65536];
                DatagramPacket reply = new DatagramPacket(buffer, buffer.length);
                sock.receive(reply);

                byte[] data = reply.getData();
                s = new String(data, 0, reply.getLength());

                //echo the details of incoming data - client ip : client port - client message
                echo(reply.getAddress().getHostAddress() + " : " + reply.getPort() + " - " + s);
            }
        }

        catch(IOException e)
        {
            System.err.println("IOException " + e);
        }
    }

    //simple function to echo data to terminal
    public static void echo(String msg)
    {
        System.out.println(msg);
    }
}

Server

import java.io.*;
import java.net.*;
import java.util.*;
class ServerSix
{
	public static void main(String[] args) throws Exception
	{
		DatagramSocket ds = new DatagramSocket(7777);
		byte[] buffer = new byte[65536];
		DatagramPacket packet = new DatagramPacket(buffer,buffer.length);
		while(true)
		{
			ds.receive(packet);
			byte[] data = packet.getData();
			String s = new String(data, 0, packet.getLength());
			String s1="";
			for(char c : s.toCharArray())
			{
				int x = (int)c;

				if(x>=65 && x<=90)
				{
				x=(((x+1)-65)%26)+65;
				s1 += Character.toString((char)x);
				}
				else if(x>=97 && x<=122)
				{
				x=(((x+1)-97)%26)+97;
				s1 += Character.toString((char)x);
				}
				else
				{
				s1 += c;
				}

			}
			echo(packet.getAddress().getHostAddress() + " : " + packet.getPort() + " - " + s1);

                s1 = "OK : " + s1;
                DatagramPacket dp = new DatagramPacket(s1.getBytes() , s1.getBytes().length , packet.getAddress() , packet.getPort());
                ds.send(dp);
		}
	}
	public static void echo(String msg)
    {
        System.out.println(msg);
    }
}

7. Write a Java program to display the name and address of the computer that we are currently
working on.

import java.net.*;
import java.io.*;
public class cm
{
public static void main(String args[])
{
try
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the url which you want to find ip address and host name");
String str=br.readLine();
InetAddress add=InetAddress.getByName(str);
System.out.println("Local Host Information");
System.out.println("Host Name:"+add.getHostName());
System.out.println("IP address:"+add.getHostAddress());
}
catch(Exception e)
{
System.out.println(e);
}
}

9. Using threading concepts, write a Java program to create a daemon process.

import java.util.*;
import java.io.*;
import java.net.*;
 public class Back extends Thread
{
public void run()
{
if(Thread.currentThread().isDaemon())
{//checking for daemon thread Â
 System.out.println("daemon thread work");
 } else{
 System.out.println("user thread work");
 }
 }
}
  class Daemon{

 public static void main(String[]Â args){
Back t1=new Back();//creating thread
 Back t2=new Back();
Back t3=new Back();
t1.setDaemon(true);//now t1 isÂdaemon thread
 t1.start();//starting threads Â
 t2.start();
 t3.start();
} }

10. A server should run for 10 secs and generate numbers continuously. The client connecting to it
should read data and find out the sum of the data thus read. Write a Java program to implement this
scenario.

Sever
import java.net.*;
import java.io.*;
class Rand extends Thread{
	DataOutputStream dout;
	public Rand(DataOutputStream d){
		dout=d;
	}
public void run(){
try{
while(true){
dout.writeInt((int)(Math.random()*100)+1);
}
}
catch(IOException e)
{}
}
}
class ServerRandom{
public static void main(String args[])throws Exception{
ServerSocket ss=new ServerSocket(1111);
Socket s=ss.accept();
DataOutputStream dout=new DataOutputStream(s.getOutputStream());
Rand r=new Rand(dout);
r.start();
Thread.sleep(3000);
System.exit(0);
}
}

client

import java.net.*;
import java.io.*;
class ClientRandom{
public static void main(String args[])
{
int sum=0;
try{
Socket s=new Socket("localhost",1111);
System.out.println("bb");
    DataInputStream din=new DataInputStream(s.getInputStream());

	while(true){
	int a=din.readInt();
	System.out.println(a);
	sum=sum+a;
	}
}
catch(Exception e){
	System.out.println("sum="+sum);
    }
}
}