RPCServer.java

import java.io.*;
import java.net.*;
import java.util.ArrayList;
import java.util.List;

public class RPCServer {
    
    private static List<String> messages = new ArrayList<>();
    
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(5000);
            System.out.println("RPC Server is running on port 5000...");
            
            while (true) {
                Socket clientSocket = serverSocket.accept();
                System.out.println("Client connected: " + clientSocket.getInetAddress());
                
                // Handle client in a new thread
                new Thread(() -> handleClient(clientSocket)).start();
            }
        } catch (IOException e) {
            System.err.println("Server error: " + e.getMessage());
            e.printStackTrace();
        }
    }
    
    private static void handleClient(Socket clientSocket) {
        try {
            BufferedReader in = new BufferedReader(
                new InputStreamReader(clientSocket.getInputStream()));
            PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
            
            String request;
            while ((request = in.readLine()) != null) {
                System.out.println("Received request: " + request);
                
                String response = processRequest(request);
                out.println(response);
                
                if (request.equals("QUIT")) {
                    break;
                }
            }
            
            clientSocket.close();
            System.out.println("Client disconnected");
            
        } catch (IOException e) {
            System.err.println("Client handler error: " + e.getMessage());
        }
    }
    
    private static String processRequest(String request) {
        String[] parts = request.split("\\|", 2);
        String method = parts[0];
        
        switch (method) {
            case "HELLO":
                String name = parts.length > 1 ? parts[1] : "Guest";
                return "Hello, " + name + "!";
                
            case "ADD":
                String[] numbers = parts[1].split(",");
                int a = Integer.parseInt(numbers[0]);
                int b = Integer.parseInt(numbers[1]);
                return String.valueOf(a + b);
                
            case "SEND":
                String message = parts.length > 1 ? parts[1] : "";
                messages.add(message);
                System.out.println("Received from client: " + message);
                return "Message received";
                
            case "GETALL":
                if (messages.isEmpty()) {
                    return "No messages";
                }
                return String.join(";;", messages);
                
            case "QUIT":
                return "Goodbye";
                
            default:
                return "Unknown method";
        }
    }
}