Http client/server example - java

Client.java

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

class Client {
    public static void main(String[] args) {
        // main thread
        System.out.println("hello from client");
        try {
            Socket socket = new Socket("localhost", 3000);

            System.out.println("connected to the server");
            System.out.println("port=" + socket.getPort());
            System.out.println("localPort=" + socket.getLocalPort());

            PrintWriter pw = new PrintWriter(socket.getOutputStream(), true);
            pw.println("GET / HTTP/1.1");

            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            String line = in.readLine(); // reads until "\n"
            System.out.println("received: " + line);

            in.close();
            socket.close();
        } catch (IOException e) {
            System.out.println("Error " + e.getMessage());
            e.printStackTrace();
        }

        System.out.println("finished");
    }
}

Server.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.time.Instant;

public class Server {
    public static void main(String[] args) {
        // main thread
        println("hello");
        new Server().run();
        println("finished");
    }

    private void run() {
        try {
            final ServerSocket server = new ServerSocket(3000);
            
            while (true) {
                println("Waiting for a client to be connected....");
                // blocks, until a client is connected
                final Socket client = server.accept();

                println("A client connected, running it inside a thread");

                new Thread(() -> {
                    println("A thread for client is started");

                    try {
                        handleClient(client);
                    } catch (IOException e) {
                        println("Client Error " + e.getMessage());
                        e.printStackTrace();            
                    }
                }).start();
            }

            // server.close();
        } catch (IOException e) {
            println("Error " + e.getMessage());
            e.printStackTrace();
        }
    }

    private void handleClient(final Socket client) throws IOException {
        println("yay, a client is connected: " + client.getInetAddress());
        println("local port: " + client.getLocalPort());
        println("port: " + client.getPort());

        BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
        String line = in.readLine();

        println("a request from client: " + line);

        String[] chunks = line.split(" ");
        String method = chunks[0];
        String path = chunks[1];
        String httpVersion = chunks[2];

        println("HTTP method=" + method);
        println("HTTP path=" + path);
        println("HTTP version=" + httpVersion);

        PrintWriter pw = new PrintWriter(client.getOutputStream(), true);

        if (path.equals("/")) {
            HomeController controller = new HomeController();
            String response = controller.get();
            pw.println("HTTP/1.1 200 OK");
            pw.println("Content-Type: text/html; charset=UTF-8");
            pw.println("Location: http://localhost/");
            pw.println();
            pw.println(response);
        } else {
            pw.println("HTTP/1.1 404 Not Found");
            pw.println("Content-Type: application/text");
        }

        pw.close();
        client.close();
    }

    static class HomeController {
        
        public String get() {
            try {
                println("computing large computation open ai");
                Thread.sleep(10_000);
                println("finished computing large llm");
            } catch (Exception e) {}

            return "<h1>My app</h1><b>hello from home controller</b>";
        }
    }

    static void println(String msg) {
        String now = Instant.now().toString();
        Thread t = Thread.currentThread();
        System.out.println(now + " - " + "[" + t.getName() + ":" + t.threadId() + "] " + msg);
    }

}