Question

look this code is a correct but i want modify it to allow the client to have three attempts to login to the server

package hw2;

import java.net.*;
import java.util.Formatter;
import java.util.Random;
import java.util.Scanner;
import java.io.*;

public class Client {
   Socket server;
   int port;
   Formatter toNet = null;
   Scanner fromNet = null;
   Scanner fromUser = new Scanner(System.in);

   public Client() {
       try {
           // login at server at local host port 4000
           server = new Socket("localhost",4000);
           System.out.println("UserName: ");
           String user = fromUser.nextLine();
           System.out.println("Password: ");
           String pass = fromUser.nextLine();
           //to dedecate with the server
           fromNet = new Scanner(server.getInputStream());
           toNet = new Formatter(server.getOutputStream());
           toNet.format("%s\n", user);
           toNet.flush();
           toNet.format("%s\n", pass);
           toNet.flush();
           String response=fromNet.nextLine();
           if(!response.equals("valid") {
               System.out.println("Invalid Login!!");
           }else {
               // if login is successful vote at local host port 4001
               server = new Socket("localhost",4001);//establish new connection
               //establish a strem
               toNet = new Formatter(server.getOutputStream());
               System.out.prinln("Enter your vote 0-9: ");
                   String vote = formUser.nextLine();
                   toNet.format("%s\n", vote);
                   toNet.flush();
           }
              
       } catch (IOException ioe) { }
   }

   public static void main(String[] args) {
           new Client();
   }
}

package hw2;
import java.net.*;
import java.util.Formatter;
import java.util.Scanner;
import java.io.*;

public class ServiceServer0 extends Thread{//login multithreaded service
   Socket client;
   Scanner fromNet = null;
   Formatter toNet = null;
   private String login[][] = { { "user1", "pass1" }, { "user2", "pass2" }, { "user3", "pass3" }, { "user4", "pass4" },
           { "user5", "pass5" }, { "user6", "pass6" }, { "user7", "pass7" }, { "user8", "pass8" },
           { "user9", "pass9" }, };
   public ServiceServer0(Socket client) {
       this.client = client;
   }
   public void run() {
       System.out.println("Login Service: Serving client ...");
       try {
           fromNet = new Scanner(client.getInputStream());
           toNet = new Formatter(client.getOutputStream());
           String user = fromNet.nextLine(); //read the user
           String pass = fromNet.nextLine(); // read the pass
           String respone = " ";
           boolena fount = false;
           for (int i=0; i<long.length; i++) {
               if(login[i][0].equals(user) && login[i][1].equals(pass)) {
                   respone="valid";
                   found = true;
                   break; // to go out from for loop
               }
           }
          
           if(!found)
               response= "Invalid";
              
           toNet.format("%s\n", response);
           toNet.flush();
          
       }catch(IOException ioe) {}  
   }
}

package hw2;
import java.net.*;
import java.util.Formatter;
import java.util.Scanner;
import java.io.*;

public class ServiceServer2 extends Thread{//other services in similar manner
   Socket client;
   Scanner fromNet = null;
   Formatter toNet = null;

   public ServiceServer2(Socket client) {
       this.client = client;
   }
   public void run() {
       System.out.println("ServiceServer2: Serving client ...");
       try {
           fromNet = new Scanner(client.getInputStream());
           toNet = new Formatter(client.getOutputStream());

          
       }catch(IOException ioe) {}
      
   }

}

Answer 1

You have multiple ways to allow 3 attemps to login

1) maintain a Map<String,Boolean> userloginattemptedmap which will conatins userid vs allowedFlag. set it false when user attemped 3 times to login.

2) simple count variable to check the attempt made.

i have described 2nd one here...For more dynamic code you can use 1st one as well.

package hw2;

import java.net.*;
import java.util.Formatter;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import java.util.Scanner;
import java.io.*;

public class Client {
Socket server;
int port;
Formatter toNet = null;
Scanner fromNet = null;
Scanner fromUser = new Scanner(System.in);
Map<String,Boolean> map=new HashMap<String,Boolean>();

public Client() {
try {
// login at server at local host port 4000
server = new Socket("localhost",9200);
//to dedecate with the server
fromNet = new Scanner(server.getInputStream());
toNet = new Formatter(server.getOutputStream());
int count=0;
while(count>=0&&count<3) {
System.out.println("UserName: ");
String user = fromUser.nextLine();
System.out.println("Password: ");
String pass = fromUser.nextLine();
  
toNet.format("%s\n", user);
toNet.flush();
toNet.format("%s\n", pass);
toNet.flush();
String response=fromNet.nextLine();
if(!response.equals("valid")) {
System.out.println("Invalid Login!!");
count++;
}else {
   count=-1;
// if login is successful vote at local host port 4001
server = new Socket("localhost",4001);//establish new connection
//establish a strem
toNet = new Formatter(server.getOutputStream());
System.out.println("Enter your vote 0-9: ");
String vote = fromUser.nextLine();
toNet.format("%s\n", vote);
toNet.flush();
}
}
if(count==3) {
   System.out.println("You have reached maximum allowed login request! please contact the Administrator");
}
  
} catch (IOException ioe) {
   ioe.printStackTrace();
}
}

public static void main(String[] args) {
new Client();
}
}