Networking problem with server

Question

Hi i a have developed a client server application,where a students logs in using agui to aestablish a connection with the server.When mu server is up and running waiting for clients and when i run my client program and the GUI appears then the folowing error appears on my server outpurt
java.lang.ArrayIndexout of bounds exception
at lines,38,69,and 151.Here is my server code
import java.io.*;
import java.net.*;
import java.util.Random;
public class Server extends Thread {
//private static final int portnumber = 4444;
private static final int waitforclient = 0;//represents when the server is idle and is waiting for a client connection
private static final int waitforanswer = 1;//
private static final int waitforconfirm = 2;//represents the server waiting for conformation from client
private ServerSocket serverSocket; //keeps up with the server-socket connection
private String[] questions;
private JDBC jdbc;
private int numQuestions; //stores the number of questions
private int num = 0; //num is the number of the current question been asked
private int state = waitforclient; //hold the cueent state of the server
private Random rand = new Random(); //pick questions at random
//creating server socket
public Server(){
super("Server");
try{
serverSocket = new ServerSocket(4444);
System.out.print("Socket created and server now waits for clients");
catch (IOException e)
System.out.print("Error:couldn't create socket");
System.exit(1);
public static void main(String[] args){
Server obj = new Server();
obj.run();
public void run(){
Socket client = null;
if (!initQnA()){
System.out.println("couldn't initialise questions");
return;
while (true){
if (serverSocket==null)
return;
try{
client = serverSocket.accept();
jdbc = new JDBC();
jdbc.getPassword();
catch(IOException e){
System.out.println("couldn't connect to client socket");
System.exit(1);
try
InputStreamReader isr =new InputStreamReader(client.getInputStream());
BufferedReader is = new BufferedReader(isr);
PrintWriter os = new PrintWriter(new BufferedOutputStream(client.getOutputStream()),false);
String outLine;
outLine = processInput(null); //communication between the client and server is handdddled by this method
os.println(outLine);
os.flush();
while (true){
String inLine = is.readLine();
if(inLine.length() > 0){
outLine = processInput(inLine);
os.println(outLine);
os.flush();
if(outLine.equals("invalid"))
break;
//Clean up
os.close();
is.close();
client.close();
catch(Exception e){
System.err.println("Exception: "+e);
e.printStackTrace();
private boolean initQnA(){
try{
File infile = new File("password.txt");
FileInputStream inStream = new FileInputStream(infile);
byte[] data = new byte[(int)infile.length()];
if (inStream.read(data) <= 0){
System.err.println("error: couldn't read file");
return false;
//used to find the number of users
for (int i=0; i< data.length; i++) {
if (data[i] == (byte)'\n') {
numQuestions++;
questions = new String[numQuestions];
//stores the users in a array called questions
int start = 0, index = 0;
for (int j=0; j< data.length; j++) {
if (data[j] == (byte)'\n'){
questions[index] = new String(data, start, j-start-1);
index++;
start =j+1;
catch (FileNotFoundException e){
System.err.println("Exception: couldn't find the question file");
return false;
catch(IOException e){
System.err.println("Exception: io error");
return false;
return true;
String processInput(String inStr){//Each case stement in process statement reperesents
                                                       //the server leaving the given state
String outStr = null;
switch (state){
case waitforclient:
outStr = questions[num];
state = waitforanswer;
break;
case waitforanswer:
outStr = "invalid";
//int con = inStr.charAt('=');
//String re = inStr.substring(0,con);
for (int y=0; y< numQuestions; y++){
System.out.println(inStr);
if (inStr.equalsIgnoreCase(questions[y])){
outStr = "valid";
System.out.println("valid user");
break; // if he is a valid user then create a txt file using his username as the name of the file
case waitforconfirm:
if (inStr.equalsIgnoreCase("stop server")){
state = waitforclient;
num = Math.abs(rand.nextInt())%
questions.length;
outStr = questions[num];
state = waitforanswer;
else{
//outStr ="Bye";
state = waitforclient;
break;
return outStr;
}

Answer 1

Line 38? I'm not about to count lines in your code. You find line 38 yourself. You'll find it has an array index taking place in it somewhere. That index is either less than zero or greater than or equal to the array size. If you want to post this again, please do us the courtesy of indicating those lines and formatting the code properly.