Echo TCP-Server (Java)

Attention.md

Echo TCP Server (Java)

Client.java

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.stream.Stream;

public class Client implements AutoCloseable {
	private final Socket client;
	private final DataOutputStream os;
	private final BufferedReader is;

	public Client(String host, int port) throws UnknownHostException, IOException {
		client = new Socket(host, port);
		os = new DataOutputStream(client.getOutputStream());
		is = new BufferedReader(new InputStreamReader(client.getInputStream()));
	}

	public void sendReceive(String message) {
		try {
			System.out.println("Thread = " + Thread.currentThread());
			System.out.println("Sending to Server: " + message);
			os.writeBytes(message + "\n");
			os.flush();
			// keep on reading from/to the socket till we receive the "Ok" from Server,
			// once we received that we break.
			String responseLine = is.readLine();
			if (responseLine != null) {
				System.out.println("Server Sent: " + responseLine);
			} else {
				System.out.println("Server Sent: No Response");
			}
		} catch (UnknownHostException e) {
			System.err.println("Don't know about host: hostname");
		} catch (IOException e) {
			System.out.println(e);
		}
	}

	public void close() throws IOException {
		sendReceive("QUIT");
		is.close();
		os.close();
	}

	public static void main(String[] args) throws UnknownHostException, IOException, InterruptedException {
		int port = 8080;
		String host = "localhost";
		int totalClients = 4;
		Stream.iterate(1, x -> x + 1).limit(totalClients).forEach(id -> {
			new Thread(() -> {
				try (Client client = new Client(host, port)) {
					client.sendReceive("HELO" + id);
					Thread.sleep(2000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				} catch (UnknownHostException e) {
					e.printStackTrace();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}).start();
		});
	}
}

Server.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;

public class Server implements AutoCloseable {
	private final ServerSocket server; 
	
	public Server(String host, int port, int backlogConnectionQueueLength) throws UnknownHostException, IOException {
		server = new ServerSocket(port, backlogConnectionQueueLength, InetAddress.getByName(host));
		System.out.println(Thread.currentThread() + " Created Server");
	}
	
	public void start() {
		System.out.println(Thread.currentThread() + " Server Ready: " + server);
		while (true) {
			acceptAndHandleClient(server);
		}
	}

	private void acceptAndHandleClient(ServerSocket server) {
		System.out.println(Thread.currentThread() + " Waiting for Incoming connections...");
		try (Socket clientSocket = server.accept()) {
			handleNewClient(clientSocket);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

  private void handleNewClient(Socket clientSocket) throws IOException {
		System.out.println(Thread.currentThread() + " Received Connection from " + clientSocket);
		BufferedReader is = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
		PrintStream os = new PrintStream(clientSocket.getOutputStream());
		// echo that data back to the client, except for QUIT.
		String line = null;
		while ((line = is.readLine()) != null) {
			System.out.println(Thread.currentThread() + " Server Got => " + line);
			if (line.equalsIgnoreCase("QUIT"))
				break;
			else {
				System.out.println(Thread.currentThread() + " Server echoing line back => " + line);
				os.println(line);
				os.flush();
			}
		}
		System.out.println(Thread.currentThread() + " Server Closing Connection by Sending => Ok");
		os.println("Ok");
		os.flush();
		is.close();
		os.close();
  }
	
	public void close() throws IOException {
		server.close();
	}
	
	public static void main(String[] args) {
		try (Server server = new Server("localhost", 8080, 50)) {
			server.start();
		} catch (IOException e) {
			System.out.println(e);
		}
	}
}