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;        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();        serverSocket.close();    }}