Question
Java help: Write a client program in Java which can interact with the server created below (see code) via the Internet (*), using the application-layer
Java help: 
Write a client program in Java which can interact with the server created below (see code) via the Internet (*), using the application-layer protocol above. The client should connect to the server and ask the user to enter user commands of the following form, using the keyboard (console): SUBMIT token, RETRIEVE and QUIT. The user can successively enter as many commands as s/he wants (in a loop), until QUIT is entered by the user, which ends the connection to the server (i.e., QUIT is sent to the server) and ends the client program. Each SUBMIT and RETRIEVE command should be immediately forwarded to the server and the client should then print the response received from the server. Dont forget to test error conditions (e.g., by submitting eleven different tokens to the server). Also, check that a single running server can deal with multiple clients (i.e., two or more running instances of your client program) simultaneously (see code below). Your client should print a log of all its interactions with the server (see example console output below). (*) Server and client(s) need to interact via TCP/IP, but for simplicity and security reasons, clients and the server should actually run on the same machine (localhost). The IP-address used to connect to the server should be 127.0.0.1. Use a port number of your own choice.
MultiThreadedServer.java
import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.IOException; import java.net.ServerSocket; import java.net.Socket; import java.util.TreeSet; /*** * Multi Threaded server maintains a list of unique tokens and gives facilities to client to add the tokens * @author Your name * */ public class MultiThreadedServer { static TreeSet lst = new TreeSet(); //shared list of tokens public static void main(String[] args) { ServerSocket server = null; try { // server is listening on port 9999 server = new ServerSocket(9999); server.setReuseAddress(true); while (true) { // socket object to receive incoming client // requests Socket client = server.accept(); //start listening // create a new thread object Handler clientSock = new Handler(client); // This thread will handle the client new Thread(clientSock).start(); } } catch(Exception e) { e.printStackTrace(); } finally { if (server != null) { try { server.close(); } catch (Exception e) { e.printStackTrace(); } } } } /*** * Individual Request handler thread * @author Your name * */ static class Handler extends Thread{ private Socket socket; public Handler(Socket socket){ this.socket=socket; } public void run() { try { //create input and output streams DataInputStream dis = new DataInputStream(socket.getInputStream()); DataOutputStream dos = new DataOutputStream(socket.getOutputStream()); while(true) {//process individual commands until client does not wants to exit String command = dis.readUTF().trim(); if(command.equals("RETRIEVE")) { //if client wants to retrieve the list if(isEmpty()) dos.writeUTF("ERROR"); else dos.writeUTF(lst+""); } if(command.equals("QUIT")) //if clinet wants to quit break; if(command.startsWith("SUBMIT")) { //append query String token[] = command.split(" "); if(contains(token[1]) || size()>=10) dos.writeUTF("ERROR"); else { add(token[1]); dos.writeUTF("OK"); } } } } catch (IOException e) { e.printStackTrace(); } } } //all the method handles concurrent modification on the shared list static synchronized void add(String s) { lst.add(s); } static synchronized void remove(String s) { lst.remove(s); } static synchronized boolean isEmpty() { return lst.isEmpty(); } static synchronized boolean contains(String s) { return lst.contains(s); } static synchronized int size() { return lst.size(); } } ClientCode.java
import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.IOException; import java.net.Socket; import java.net.UnknownHostException; import java.util.Scanner; /*** * Client class to connect to server running on 9999 * @author Your name * */ public class ClientCode { public static void main(String[] args) throws UnknownHostException, IOException { Socket s = new Socket("localhost",9999); //connect to server System.out.println("Client: connected to server"); DataInputStream dis = null; DataOutputStream dos = null; //create streams dis = new DataInputStream(s.getInputStream()); dos = new DataOutputStream(s.getOutputStream()); Scanner sc = new Scanner(System.in); String command; //read each command and send it to server until user wants to exit do { command = sc.nextLine(); command = command.toUpperCase(); dos.writeUTF(command); if(command.equals("QUIT")) break; System.out.println("Client: sent '"+command+"' to server"); String ans = dis.readUTF(); System.out.println("Client: recieved message from server '"+ans+"'"); }while(true); s.close(); sc.close(); } } 
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AWS Certified Database Study Guide Specialty DBS-C01 Exam
Authors: Matheus Arrais, Rene Martinez Bravet, Leonardo Ciccone, Angie Nobre Cocharero, Erika Kurauchi, Hugo Rozestraten
1st Edition
1119778956, 978-1119778950
