#Need help (Basic Local Socket Programming)

9 messages · Page 1 of 1 (latest)

still patrol
#

Got a program here I've been writing, just a basic addition that the client responds to, but it seems that I don't have a concrete understand of DataInputStream & DataOutputStream methods like writeUTF() or flush(). I have the code that I'm trying to implement commented but whenever I run it, when the user reaches the second problem, the server crashes.

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Random;
//SERVER

public class BasicAdditionServer
{
    int operand1;
    int operand2;
    int sum;
    int correct;
    int incorrect;
    int questionNum = 0;


    public static void main(String[] args) throws IOException {
        ServerSocket se = new ServerSocket(9999);
        Socket so = se.accept();
        System.out.println("Client Connected.");

        BasicAdditionServer bas = new BasicAdditionServer();

        DataInputStream dis = new DataInputStream(so.getInputStream());
        DataOutputStream dos = new DataOutputStream(so.getOutputStream());

        String str = "";
        String resp = "";

        while (bas.questionNum < 10 || str.equals("stop"))
        {
            for(int z = 0; z < 10; z++)
            {
                resp = "";
                //dos.writeUTF(bas.genCalc());
                dos.writeUTF("[SERVER] - " + bas.genCalc());
                dos.flush();
                str = dis.readUTF();

                if (bas.sum == Integer.parseInt(str))
                {
                    bas.correct++;
//                    resp = "\nCORRECT!";
//                    dos.writeUTF(resp);
//                    //dos.flush();


                }
                else
                {
                    bas.incorrect++;
//                    resp = "\nINCORRECT. CORRECT ANSWER --> " + bas.sum;
//                    dos.writeUTF(resp);
//                    //dos.flush();
                }

            }
            //str = dis.readUTF();

            //dos.writeUTF(str);
            dos.writeUTF(bas.progressResult());
            dos.flush();
            /*
            When you write data to a stream, it is not written immediately, and it is buffered.
            So use flush() when you need to be sure that all your data from buffer is written.
            We need to be sure that all the writes are completed before we close the stream,
            and that is why flush() is called in file/buffered writer's close()
            */
        }
        dos.close();
        dis.close();
        so.close();
        se.close();
        System.out.println("[SERVER DISCONNECTED]");
    }

    public String genCalc()
    {
        sum = 0;
        questionNum++;
        String result = "";
        Random rand = new Random();
        operand1 = rand.nextInt(1,10);
        operand2 = rand.nextInt(1,10);
        sum = (operand1 + operand2);
        result = ("[Question " + questionNum + "]: " + operand1 + " + " + operand2 + "?" );
        return result;
    }

    public String progressResult()
    {
        return "[---RESULTS---] \n \n[CORRECT]: " + correct + "    [INCORRECT]: " + incorrect + "\n\nPRESS ENTER TO EXIT... ";

    }
}
kindred oxideBOT
#

⌛ This post has been reserved for your question.

Hey @still patrol! Please use /close or the Close Post button above when your problem is solved. Please remember to follow the help guidelines. This post will be automatically closed after 300 minutes of inactivity.

TIP: Narrow down your issue to simple and precise questions to maximize the chance that others will reply in here.

still patrol
#

(My client program)

import java.io.*;
import java.net.Socket;
import java.util.Scanner;

public class BasicAdditionClient
{
    public static void main(String[] args) throws IOException
    {
        int questionCounter = 0;
        Socket soc = new Socket("localhost", 9999);

        Scanner keyboard = new Scanner(System.in);

        DataInputStream di = new DataInputStream(soc.getInputStream());
        DataOutputStream dout = new DataOutputStream(soc.getOutputStream());

        //Read text from a character-input stream,
        //buffering characters to provide for the efficient reading of characters,
        //arrays, and lines.
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

        String userInput=""; //getItBack="";

        while(questionCounter < 11)
        {
            System.out.println(di.readUTF());
            userInput = br.readLine();

            dout.writeUTF(userInput);
            dout.flush();
            //getItBack = di.readUTF();
            //System.out.println("echo: " + getItBack);
            questionCounter++;

        }

        dout.close();
        di.close();
        soc.close();
    }

}
cedar dragon
#

I have copy/pasted that code and nothing crashes

still patrol
#

Im trying to figure out why

cedar dragon
#

Y'know, we've all been beginners but I've never been someone to whom it would occur doing something like that

#

I imagine your client code is different too?