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Thread: Java Server Guessing Game

  1. #1
    Junior Member
    Join Date
    Dec 2012
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    Default Java Server Guessing Game

    I'm a self confessed noob so don't be too harsh if there's a idiotic mistake! To put it simply I'm creating a server where clients connect to play a guessing game they are also to get points from doing this. My only problem at the moment is that whenever my client guesses the number correctly it jumps to the server and says 'server null' I want the guessing game to continue until the client inputs 'goodbye' - on which his/her score is given. Here is my code could you point out where I've gone wrong and advise me on how I would achieve what I want. I think the problem is in protocol I probably just need to put the while in the correct place, so that's up first. Thanks folks!
    Just to add the variables are named oddly I'm aware of this it was previously a knock knock joke server

    import java.util.*;
            public class KKProtocol {
        int guess = 0, number = new Random().nextInt(100) + 1;
        int score = 0;
        Scanner scan = new Scanner(System.in);
        public String processInput(String theInput) {
            String theOutput = null;
            System.out.println("Please guess the number between 1 and 100.");
            while (guess != number) {
              try {
                if ((guess = Integer.parseInt(scan.nextLine())) != number) {
                  System.out.println(guess < number ? "Higher..." : "Lower...");
                else {
                  score = 1;
              catch (NumberFormatException e) {
                System.out.println("Please enter a valid number! If you want to Quit just say'Goodbye'");
            return theOutput;   
    import java.net.*;
    import java.io.*;
    public class KKServer {
        public static void main(String[] args) throws IOException {
            ServerSocket serverSocket = null;
            boolean listening = true;
            try {
                serverSocket = new ServerSocket(4040);
            } catch (IOException e) {
                System.err.println("Could not listen on port: 4040.");
            System.err.println("Started KK server listening on port 4040");
            while (listening)  
                new KKThread(serverSocket.accept()).start();
                System.out.println("Accepted connection from client");
    import java.net.*;
    import java.io.*;
    import java.util.Scanner;
    public class KKThread extends Thread {
        private Socket mySocket = null;
        public KKThread(Socket inSocket) {           //super("KKThread");
            mySocket = inSocket;
        public void run() {
            try {
                PrintWriter out = new PrintWriter(mySocket.getOutputStream(), true);
                Scanner in = new Scanner(mySocket.getInputStream());
                String inputLine, outputLine;
                KKProtocol kkp = new KKProtocol();
                outputLine = kkp.processInput(null);        // first time only
                out.println(outputLine);        // (Should be "Knock Knock")
                while (true) {
                    inputLine = in.nextLine();                  // read in client input
                    outputLine = kkp.processInput(inputLine);   // get reply from protocol
                    out.println(outputLine);                    // send it out to socket
                    if (outputLine.equals("Bye"))
            } catch (Exception e) {
                System.err.println("Connection reset");  //e.printStackTrace();
    import java.io.*;
    import java.net.*;
    import java.util.Scanner;
    public class KKClient {
        public static void main(String[] args) throws IOException {
            Socket kkSocket = null;
            PrintWriter out = null;
            Scanner in = null;
            try {
                kkSocket = new Socket("", 4040);
                out = new PrintWriter(kkSocket.getOutputStream(), true);
                in = new Scanner(new InputStreamReader(kkSocket.getInputStream()));
            } catch (UnknownHostException e) {
                System.err.println("Don't know about host.");
            } catch (IOException e) {
                System.err.println("Couldn't get I/O for the connection");
            Scanner stdIn = new Scanner(System.in);
            String fromServer = in.nextLine();
            while (true) {
                System.out.println("Server: " + fromServer);
                if (fromServer.equals("Bye."))
                fromServer = in.nextLine();

  2. #2
    Super Moderator Norm's Avatar
    Join Date
    May 2010
    Eastern Florida
    Thanked 2,455 Times in 2,406 Posts

    Default Re: Java Server Guessing Game

    says 'server null'
    What is the "it" that says that? Is there an error or is there a print statement in the code that prints that message?
    Is this the statement:
    System.out.println("Server: " + fromServer);
    Was the message that was printed: Server: null?

    That would mean that fromServer has a null value.

    Can you post the full contents of the console from when you execute the program.

    To copy the contents of the command prompt window:
    Click on Icon in upper left corner
    Select Edit
    Select 'Select All' - The selection will show
    Click in upper left again
    Select Edit and click 'Copy'

    Paste here.
    If you don't understand my answer, don't ignore it, ask a question.

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