Mutual Exclusion Using Token Ring Algorithm

Mutual Exclusion Using Token Ring Algorithm

PROBLEM STATEMENT:

     Write a program to apply mutual exclusion using Token Ring algorithm. The program contains two or more clients and a server. Token is circulated among all client sequentially, a client which has token has right to send message to the server.

DESCRIPTION:

       In this algorithm, a logical ring is constructed in which each process is assigned a position in the ring. Initially a process 0 is given the token. The token circulates around the ring.
    When a process acquires token from its neighbor, it checks to see if it is attempting to enter a critical region. If so, the process enters the region, finishes its work and then leaves the region. Then, it passes the token along the ring.
    If the process is handed the token by its neighbor and is not interested in entering a critical region, it just passes it along.

SOURCE CODE:

TokenServer.java

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

public class TokenServer
{
    public static void main(String agrs[])throws Exception
        {
           
            while(true)
            {
            Server sr=new Server();
            sr.recPort(8000);
            sr.recData();
            }
        }
}

class Server
{
   
    boolean hasToken=false;
    boolean sendData=false;
    int recport;
   
    void recPort(int recport)
    {
        this.recport=recport;
    }

    void recData()throws Exception
    {
        byte buff[]=new byte[256];
        DatagramSocket ds;
        DatagramPacket dp;
        String str;
       
        ds=new DatagramSocket(recport);
        dp=new DatagramPacket(buff,buff.length);
        ds.receive(dp);
        ds.close();
       
        str=new String(dp.getData(),0,dp.getLength());
        System.out.println("The message is "+str);
    }
}

TokenClient1.java

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

public class TokenClient1
{
    public static void main(String arg[]) throws Exception
        {
            InetAddress lclhost;
            BufferedReader br;
            String str="";
            TokenClient12 tkcl,tkser;
            boolean hasToken;
            boolean setSendData;
           
            while(true)
            {
            lclhost=InetAddress.getLocalHost();
            tkcl = new TokenClient12(lclhost);
            tkser = new TokenClient12(lclhost);       
            //tkcl.setSendPort(9001);
            tkcl.setSendPort(9004);
            tkcl.setRecPort(8002);
            lclhost=InetAddress.getLocalHost();
            tkser.setSendPort(9000);

            if(tkcl.hasToken == true)
            {
               
System.out.println("Do you want to enter the Data --> YES/NO");
                br=new BufferedReader(new InputStreamReader(System.in));
                str=br.readLine();
                if(str.equalsIgnoreCase("yes"))
                {  
                    System.out.println("ready to send");
                    tkser.setSendData = true;
                    tkser.sendData();
                    tkser.setSendData = false;
                }
                else if(str.equalsIgnoreCase("no"))
                {
                    System.out.println("i m in else");
                    //tkcl.hasToken=false;
                    tkcl.sendData();
                    tkcl.recData();
                System.out.println("i m leaving else");
                }
            }
            else
            {
            System.out.println("ENTERING RECEIVING MODE...");
                tkcl.recData();
            }
    }
}

}       

           
class TokenClient12
{
    InetAddress lclhost;
    int sendport,recport;
    boolean hasToken = true;
    boolean setSendData = false;
    TokenClient12 tkcl,tkser;
    TokenClient12(InetAddress lclhost)
    {
       
        this.lclhost = lclhost;
    }
   
    void setSendPort(int sendport)
    {
        this.sendport = sendport;
    }

    void setRecPort(int recport)   
    {
        this.recport = recport;
    }

   
void sendData() throws Exception
        {
        BufferedReader br;
        String str="Token";
        DatagramSocket ds;
        DatagramPacket dp;
       
   
        if(setSendData == true)
        {
            System.out.println("sending ");
            System.out.println("Enter the Data");
            br=new BufferedReader(new InputStreamReader(System.in));
            str = "ClientOne....." + br.readLine();
            System.out.println("now sending");
                   
        }
            ds = new DatagramSocket(sendport);
            dp = new DatagramPacket(str.getBytes(),str.length(),lclhost,sendport-1000);
            ds.send(dp);
            ds.close();
            setSendData = false;
            hasToken = false;
    }
   
    void recData()throws Exception
    {
        String msgstr;
        byte buffer[] = new byte[256];
        DatagramSocket ds;
        DatagramPacket dp;

        ds = new DatagramSocket(recport);
        dp = new DatagramPacket(buffer,buffer.length);
        ds.receive(dp);
        ds.close();
        msgstr = new String(dp.getData(),0,dp.getLength());
        System.out.println("The data is "+msgstr);
       
        if(msgstr.equals("Token"))
            {
                hasToken = true;
            }
    }
   
}
       
           

TokenClient2.java

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

public class TokenClient2
{
    static boolean setSendData ;
    static boolean hasToken ;
    public static void main(String arg[]) throws Exception
        {
            InetAddress lclhost;
            BufferedReader br;
            String str1;
            TokenClient21 tkcl;
            TokenClient21 ser;
            while(true)
            {
            lclhost=InetAddress.getLocalHost();
            tkcl = new TokenClient21(lclhost);
            tkcl.setRecPort(8004);       
            tkcl.setSendPort(9002);
            lclhost=InetAddress.getLocalHost();
            ser = new TokenClient21(lclhost);
            ser.setSendPort(9000);
            System.out.println("entering if");   
            if(hasToken == true)
            {
               
System.out.println("Do you want to enter the Data --> YES/NO");
                br=new BufferedReader(new InputStreamReader(System.in));
                str1=br.readLine();
                if(str1.equalsIgnoreCase("yes"))
                {   
                    System.out.println("ignorecase");
                    ser.setSendData = true;
                    ser.sendData();
                    }
                else if(str1.equalsIgnoreCase("no"))
                {
                    tkcl.sendData();
                    hasToken=false;
                }
            }
            else
            {
            System.out.println("entering recieving mode");   
                tkcl.recData();
                hasToken=true;
            }
        }
    }
}
class TokenClient21
{
    InetAddress lclhost;
    int sendport,recport;
    boolean setSendData = false;
    boolean hasToken = false;
    TokenClient21 tkcl;
    TokenClient21 ser;

   
    TokenClient21(InetAddress lclhost)
    {
       
        this.lclhost = lclhost;
    }
   
    void setSendPort(int sendport)
    {
        this.sendport = sendport;
    }

    void setRecPort(int recport)   
    {
        this.recport = recport;
    }

    void sendData() throws Exception
    {
        System.out.println("case");
        BufferedReader br;
        String str="Token";
        DatagramSocket ds;
        DatagramPacket dp;
       
        if(setSendData == true)
        {
            System.out.println("Enter the Data");
            br=new BufferedReader(new InputStreamReader(System.in));
            str = "ClientTwo....." + br.readLine();
        }
            ds = new DatagramSocket(sendport);
            dp = new DatagramPacket(str.getBytes(),str.length(),lclhost,sendport-1000);
            ds.send(dp);
            ds.close();
            System.out.println("Data Sent");
            setSendData = false;
            hasToken = false;
       
    }
   
   

void recData()throws Exception
    {
        String msgstr;
        byte buffer[] = new byte[256];
        DatagramSocket ds;
        DatagramPacket dp;
ds = new DatagramSocket(recport);
        //ds = new DatagramSocket(4000);
        dp = new DatagramPacket(buffer,buffer.length);
        ds.receive(dp);
        ds.close();
msgstr = new String(dp.getData(),0,dp.getLength());
        System.out.println("The data is "+msgstr);
        if(msgstr.equals("Token"))
            {
                hasToken = true;
            }
    }
   
}
       

OUTPUT :

TokerServer.java

C:\Documents and Settings\Nids\Desktop\DCpracs\TokenRIng_prac5\final>java TokenS
erver
The message is ClientOne.....hello
The message is ClientTwo.....hii

TokelClient1.java

C:\Documents and Settings\Nids\Desktop\DCpracs\TokenRIng_prac5\final>java TokenC
Client1
Do you want to enter the Data --> YES/NO
yes
ready to send
sending
Enter the Data
hello
now sending
Do you want to enter the Data --> YES/NO
no
i m in else

TokenClient2.java

C:\Documents and Settings\Nids\Desktop\DCpracs\TokenRIng_prac5\final>java TokenC
lient2
entering if
entering recieving mode
The data is Token
entering if
Do you want to enter the Data --> YES/NO
yes
ignorecase
case
Enter the Data
hii
Data Sent
entering if
Do you want to enter the Data --> YES/NO