Main.java

import com.google.common.base.Throwables;

import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Main {

    private static final ExecutorService executor = Executors.newFixedThreadPool(5);

    public static void main(String[] args) throws IOException {
        new Main().listen();
    }

    private void listen() throws IOException {
        ServerSocket servSoc = new ServerSocket(1200);
        while (true) {
            acceptConnection(servSoc);
            System.out.println("Opened socket");
        }
    }

    private void handleSocket(Socket soc) {
        try {
            InputStreamReader isr = new InputStreamReader(soc.getInputStream());
            while (true) {
                if (soc.isClosed()) {
                    isr.close();
                    System.out.println("Socket closed");
                    return;
                }

                recvData(soc, isr);
                System.out.println();
            }
        } catch (Exception e) {
            throw Throwables.propagate(e);
        }
    }

    private void acceptConnection(ServerSocket servSoc) throws IOException {
        Socket socket = servSoc.accept();
        executor.submit(() -> handleSocket(socket));
    }

    private void recvData(Socket soc, InputStreamReader isr) throws IOException {
        waitForData(soc, isr);
        while (true) {
            int read = isr.read();
            if (read == -1) {
                soc.close();
                return;
            }
            System.out.print(Character.toChars(read));
        }
    }

    private void waitForData(Socket soc, InputStreamReader isr) throws IOException {
        while (!isr.ready() && !soc.isClosed()) {}
        return;
    }
}