Stop and Wait in Java

Client

import java.io.*;

import java.net.*;

import java.util.*;

class Clientstop

{              public static void main(String args[])

                {try{while(true)

                                {String str1=null;

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

                                Socket clsct=new Socket("127.0.0.1",139);

                                DataInputStream din=new DataInputStream(clsct.getInputStream());

                                DataOutputStream dout=new DataOutputStream(clsct.getOutputStream());

                                System.out.println("Enter the frame:");

                                String str=in.readLine();

                                dout.writeBytes(str+'\n');

                                clsct.setSoTimeout(5000);

                                str1=din.readLine();

                                System.out.println(str1);

                                clsct.close();          }}

                catch (Exception e)

                {System.out.println(e);}}}

Server

import java.io.*;

import java.net.*;

import java.util.*;

class Serverstop

{public static void main(String args[])

                {try{       String s="0";

                                int count=0;

                                ServerSocket obj=new ServerSocket(139);

                                while(true)

                                {              Socket obj1=obj.accept();

                                                DataInputStream din=new DataInputStream(obj1.getInputStream());

                                                DataOutputStream dout=new DataOutputStream(obj1.getOutputStream());

                                                String str=din.readLine();

                                                if(count==0)

                                                {              count+=1;

                                                                if(str.equals("0"))

                                                                {              s="1";

                                                                                dout.writeBytes("send frame no "+s+'\n');                      }

                                                                else if(str.equals("1"))

                                                                {              s="0";                                                    

                                                                                dout.writeBytes("send frame no "+s+'\n');                      }

                                                                else if(str.equals("-1"))

                                                                                break;

                                                }

                                                else

                                                {              count+=1;

                                                                if(str.equals(s))

                                                                {              if(str.equals("0"))

                                                                                {              s="1";

                                                                                                dout.writeBytes("send frame no "+s+'\n');      }

                                                                                else if(str.equals("1"))

                                                                                {              s="0";                                                    

                                                                                                dout.writeBytes("send frame no "+s+'\n');      }}

                                                                else if(str.equals("-1"))

                                                                                break;                    }                              }

                                obj.close();            }

                catch(Exception e)

                {              System.out.println(e);         }

                }

}

Output

Client

Enter the frame:

1

send frame no 0

Enter the frame:

0

send frame no 1

Enter the frame:

1

send frame no 0

Enter the frame:

0

send frame no 1

Enter the frame:

1

send frame no 0

Enter the frame:

-1