Program $1$:

Consider the following two programs. Write and execute them. $($You can use line commands to execute the programs or run two Eclipse programs$).$

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

import java.util.Scanner;

public class Server$\{$

public static void main$($String argv$[])$ throws Exception$\{$

$/*1.$connection$*/$

ServerSocket serverSocket $=$ new ServerSocket$(6789)$;

Socket connectionSocket $=$ serverSocket.accept$()$;

$/*2.$ A scanner or a BufferedReader for reading from the socket $*/$

Scanner scanner $=$ new Scanner$($connectionSocket$.$getInputStream$())$;

$/*3.$ A DataOutputStream object to write in the socket$*/$

DataOutputStream outToClient$=$new DataOutputStream$($connectionSocket$.$getOutputStream$())$;

$/*4.$ reading from the socket$*/$

String clientSentence $=$ scanner.nextLine$()$;

System.out.println$("$Received: $"+$ clientSentence$)$;

$/*5.$ modification of the sentence$*/$

String modifiedSentence $=$clientSentence.toUpperCase$()$;

$/*6.$ writing in the socket$*/$

outToClient.writeBytes$($modifiedSentence$+\text{'}$

$\text{'})$;

$/*7.$closing connections$*/$

scanner.close$()$;

connectionSocket.close$()$;

$\}\}$

import java.io$.*$;

import java.net.$*$;

import java.util.Scanner;

public class Client$\{$

public static void main$($String argv$[])$ throws Exception $\{$

$/*1.$ Connection$*/$

Socket connectionSocket $=$ new Socket $("$localhost$",6789)$;

Scanner scanner, scannerFromSocket;

DataOutputStream outToServer;

String sentenceFromServer;

String clientSentence;

$/*2.$ Scanner to read from keyboard $*/$

scanner $=$ new Scanner$($System$.$in$)$;

$/*3.$ Scanner to read from the socket $*/$

scannerFromSocket $=$ new Scanner$($connectionSocket$.$getInputStream$())$;

$/*4.$ DataOutputStream to write in the socket $*/$

outToServer $=$ new DataOutputStream$($connectionSocket$.$getOutputStream$())$;

$/*5.$ receiving and sending messages$*/$

clientSentence $=$scanner.nextLine$()$;

outToServer.writeBytes$($clientSentence $+\text{'}$

$\text{'})$;

sentenceFromServer$=$scannerFromSocket.nextLine$()$;

System.out.println$($sentenceFromServer$)$;

scannerFromSocket.close$()$;

scanner.close$()$;

connectionSocket.close$()$;

$\}\}$

$1.$ What happens if you execute the client program before the server one?

$2.$ Add a loop to the programs to make it repeat the task many times.

$3.$ Modify the programs to create a chat between the server and the client: The client sends a text to the server. The server prints the received text and sends an answer to the client. Use a loop to repeat the task