ahmed3415 0 Newbie Poster

Hi there,

I need help with my assignment it has to do with Client-server programming and the following is what i have been asked to do for this assignment. So far i have the server reading from the file and the client is able to read the contents of the file which server reads. I would like to know how I should to using the hash map with array list as a data structure to read the messages sent from the client and store them with in the data structure of the specific account. I am looking for some help on how I should be integrating the hash map array list in the code. Following is what my assignment is asking for:

In this assignment, you will implement a multi-user messaging system.
• The server must be implemented in Java
• You will provide two functionally equivalent clients implemented in Python and Java.

The client:

The message client is a program used to send and receive messages. The user invokes the client from command line and passes a number of parameters.

The client can:
• create an account on the server.
• send a message to an account on the server.
• check for messages for an account on the server.

The Java client:

You will implement a single Java executable class, jclient, which will be the message client. Its usage is:

Usage:

java jclient <host> <port> create <name>
Instructs the server running on the <host> at port <port> to create an account with the name <name>. If the account already exists, then the server should print an error, otherwise, the server should prints a confirmation.

java jclient <host> <port> send <name>
Instructs the server running on <host> at <port> to send a message to the account <name>. The client reads from standard input the message. Hint: You may test the send feature using redirection from an input file.
Note: the server can save multiple messages to the same account.

java jclient <host> <port> receive <name>
This retrieves all the messages stored on the server for the account <name>. The messages will be purged on the server after they are retrieved once.

The server:
The server is an executable Java class, jserver. jserver accepts network connection at a specific port, and manages messages for different accounts. The server must be multi-threaded to support simultaneous connections from different clients. The usage for the

server is:

java jserver <port>
The server must utilize the following features of Java:
• Sockets for network communication
• Java collection library for managing messages
• Threads for concurrent processing of messages
• Synchronization to handle concurrent access of common data structures

The following code is what i have done so far:

jServer.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Vector;


public class jServer {
	public static void main(String[] args) {
		try {
			/*
			 * Loading the file content into memory
			 */
			Vector<String> fileContent = new Vector<String>();
			BufferedReader fileReader = new BufferedReader(new FileReader("mydatabase"));
			String line = fileReader.readLine();
			while(line != null) {
				fileContent.add(line);
				line = fileReader.readLine();
			}
			fileReader.close();
			
			/*
			 * Starts a network server
			 */
			ServerSocket server = new ServerSocket(2000);
			Vector<Connection> clientList = new Vector<Connection>();
			while(true) {
				Socket conn = server.accept();
				Connection client = new Connection(conn, fileContent);
				clientList.add(client);
				client.start();
			}
			//server.close();
		} catch(Exception e) {
			System.out.println("Error: " + e.getMessage());
		}
	}
}

Connection.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Vector;

public class Connection extends Thread {
	private Socket conn;
	private Vector<String> fileContent;
	
	public Connection(Socket socket, Vector<String> fileContent) {
		this.conn = socket;
		this.fileContent = fileContent;
	}

	public void run() {
		System.out.println("New connection established.");
		try {
			BufferedReader reader = new BufferedReader(new InputStreamReader(
					conn.getInputStream()));
			PrintWriter writer = new PrintWriter(conn.getOutputStream());
			Client: while (true) {
				if(Thread.interrupted())
					break;
				String command = reader.readLine();
				System.out.println("> " + command);
				String[] commands = command.split(" ");
				if (commands[0].equals("read")) {
					int lineno = Integer.parseInt(commands[1]);
					if (lineno < fileContent.size() && lineno >= 0) {
						writer.println(fileContent.get(lineno));
						writer.flush();
					} else {
						writer.println("Invalid line number.");
						writer.flush();
					}
				} else if (commands[0].equals("bye")) {
					writer.println("Disconnecting...");
					writer.flush();
					break Client;
				} else {
					writer.println("Unknown command \"" + commands[0] + "\"");
					writer.flush();
				}
			}
			conn.close();

		} catch (IOException e) {
			System.out.println("IO Exception occurred: " + e.getMessage());
		}
		System.out.println("Connection closed.");
	}
}

jClient.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;


public class jClient {
	public static void main(String[] args) {
		try {
			Socket conn = new Socket(args[0], Integer.parseInt(args[1]));
			BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
			PrintWriter writer = new PrintWriter(conn.getOutputStream());
			BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
			
			while(true) {
				System.out.print("> ");
				String command = input.readLine();
				try {
					writer.println(command);
					writer.flush();
					String reply = reader.readLine();
					System.out.println("--> " + reply);
				} catch(Exception e) {
					System.out.println("Connection is lost.");
					break;
				}
			}
			conn.close();
		} catch(Exception e) {
			System.out.println("Error: " + e.getMessage());
		}
	}
}

Thanks in Advance.

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