import java.net.*;
import java.io.*;

public class KnockKnockServer {
    public static void main(String[] args) throws IOException {
		
		ServerSocket serverSocket = null;
		try {
			serverSocket = new ServerSocket(4444);
		} catch (IOException e) {
			System.err.println("Could not listen on port: 4444.");
			System.exit(1);
		}
		
		Socket clientSocket = null;
		while (true) {
			try {
				clientSocket = serverSocket.accept();
			} catch (IOException e) {
				System.err.println("Accept failed.");
				System.exit(1);
			}
			
			PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
			BufferedReader in = new BufferedReader(
				new InputStreamReader(
													  clientSocket.getInputStream()));
			String inputLine, outputLine;
			KnockKnockProtocol kkp = new KnockKnockProtocol();
			
			outputLine = kkp.processInput(null);
			out.println(outputLine);
			
			while ((inputLine = in.readLine()) != null) {
				outputLine = kkp.processInput(inputLine);
				out.println(outputLine);
				if (outputLine.equals("Bye."))
					break;
			}
			out.close();
			in.close();
			clientSocket.close();
		}
	}
}