Desperately need Java network programming help!!!

I need to make a Distributed File Sharing System (DFSS) using java language. The system should not make use of the central file server. The system should coordinate the concurrent access of files over the distributed environment. Caching may be used to enhance the system performance.
It is basically network programming.
Does any one have any idea how to make the DFSS. If you do please help!!!
thank you in advance for you help
cheers

well, you're getting somewhere I guess. My original answer was intentionally vague because your original question was so vague. These fora are no good for asking questions like "how do I implement a distributed file system", they are good for asking things like "the following line(s) of code generate the following condition I didn't expect, rather I expected this condition, could someone tell me what is going on?" or something of similar specificity.
So you are now asking how to, for instance, check to see if a text file is being shared. This is still too vague, but it's better than "how do I write a file sharing system". If you are feeling particularly industrious, go look at a project JXTA at http://www.jxta.org/ - it's open source, you can look at the code. Of course, if you're brand new, this might not help. In fact, not to discourage you, but if you're that new, this is not the project to be doing.
Good Luck
Lee

Similar Messages

Advanced Java network programming

I have been playing around with the various Server/Client tutorials not only on this site but many others for some time now. Whilst I have learnt a great deal I am now trying to further my knowledge.
The problem is, there does not seem to be a great deal of information on the Web realting to the advanced network programming stuff. Obviously not having a network of my own I am now interested in learning various ideas using the Internet. Obviously not being a prat about it and port scanning other computers or anything like that.
I was hoping someone reading this might have a suggestion about where to go next in my learning curve. Also if anyone could recommend any good sources of info for this type of stuff.
I've currently got three telephone lines in, each line with a seperate Internet account set-up. What I want to do is have them all connected to the web at once and then attempt various things, such as connection, that type of stuff.
Help really appreciated.
Thanks,
kP

Maybe I'm catching the wrong vibe here, but it seems to me that you need to learn a bit about networking in general, before you worry about how it's all done in java. I would suggest a good basic computer networking text book. After you have good understanding of how different networks works, packet structure of the various common protocols, IP, TCP over IP and UDP over IP. I think the java code to implement it all will just fall into place. my AIM SN is SpinozaQ if you would like a book suggestion. I don't have any names going through my head right now.

Where can I find knowledge about "java network programming"?

I am interested in network programming in java. I need some documents and I don't where can I find it?

http://java.sun.com/docs/books/tutorial/networking/index.html

Help needed for java network programming

How can I implement a GUI as a client in my server-client program.
I have a window(JFrame)having one Textfield and a "Send" button.
My requirement: While execution, the GUI should start as a client, and whatever textinput I will give to the Textfield, that should be printed in the server program.
So, how can I implement a GUI window as a client.
If any of U have idea,Please let me know soon.
Regards.

Well, the client part and the GUI part are separate. The button simply calls a send method.
As for the networking, you can just use a Socket and a ServerSocket on the client and server, respectively. Then, wrap a PrintStream around one side and a BufferedReader(InputStreamReader()) around the other. You'll be able to talk back and forth once your connection is established; it's up to you to read from the BufferedReader and use the results on the server side.

New to Java Wireless Programming - Help needed!

I'm currently finishing my 4 java programmign class in university, and i'm not looking to expand my knowledge in the this language. I would like to learn the how to code for wireless devices. I've already downloaded the Java Wireless Toolkit, but I would really appreciate some direction on what I should read to know where to start with this. Any info that anyone may have is greatly appreciated!
Thanks
Al

Googling J2ME tutorials or MIDP tutorials will give you plenty to read.
but here's a start:
http://www.developer.com/java/j2me/article.php/10934_1561591_1
http://developers.sun.com/techtopics/mobility/midp/samples/index.html#getstart

Network programming help required

Hi there.
I found an example of a radias calculator program that sends results to and from the client/multi threaded server.
I am trying to ammend it so I can send text to server, and echos that back to the client.
So far I am not having much luck at all trying to get this to work. I have seen examples in the tutorial, but I find them radically complicated.
If any experts out there could correct the below, that would be great!!
thanks
CLIENT
// Client.java: The client sends the input to the server and receives
// result back from the server
import java.io.*;
import java.net.*;
public class Client
// Main method
public static void main(String[] args)
try
     BufferedReader ar = null;
     BufferedWriter wr = null;
// Create a socket to connect to the server
Socket connectToServer = new Socket("localhost", 8000);
// Socket connectToServer = new Socket("bellamy.armstrong.edu", 8000);
          //ar = new BufferedReader(new InputStreamReader(new FileInputStream(UserName+ ".txt")));
// Create an input stream to receive data from the server
//DataInputStream isFromServer = new DataInputStream(connectToServer.getInputStream());
          ar = new BufferedReader(new InputStreamReader(connectToServer.getInputStream()));
// Create an output stream to send data to the server
//DataOutputStream osToServer = new DataOutputStream(connectToServer.getOutputStream());
wr = new BufferedWriter(new OutputStreamWriter(connectToServer.getOutputStream()));
// Continuously send radius and receive area from the server
while (true)
// Read the radius from the keyboard
System.out.print("Please enter a radius: ");
//double radius = 5574.5587;     //MyInput.readDouble();
String radius = "55745587";     //MyInput.readDouble();
// Send the radius to the server
//osToServer.write();
//osToServer.flush();
wr.write(radius);
wr.flush();
// Get area from the server
//String area = isFromServer.read("dsds");
String area = ar.read(" ");
// Print area on the console
System.out.println("Area received from the server is "
+ area);
catch (IOException ex)
System.err.println(ex);
MULTI THREADED SERVER
// MultiThreadsServer.java: The server can communicate with
// multiple clients concurrently using the multiple threads
import java.io.*;
import java.net.*;
public class MultiThreadServer
// Main method
public static void main(String[] args)
try
// Create a server socket
ServerSocket serverSocket = new ServerSocket(8000);
// To number a client
int clientNo = 1;
while (true)
// Listen for a new connection request
Socket connectToClient = serverSocket.accept();
// Print the new connect number on the console
System.out.println("Start thread for client " + clientNo);
// Find the client's hostname, and IP address
InetAddress clientInetAddress = connectToClient.getInetAddress();
System.out.println("Client " + clientNo + "'s hostname is "
+ clientInetAddress.getHostName());
System.out.println("Client " + clientNo + "'s IP Address is "
+ clientInetAddress.getHostAddress());
// Create a new thread for the connection
HandleAClient thread = new HandleAClient(connectToClient, clientNo);
// Start the new thread
thread.start();
// Increment clientNo
clientNo++;
catch(IOException ex)
System.err.println(ex);
// Define the thread class for handling a new connection
class HandleAClient extends Thread
private Socket connectToClient; // A connected socket
private int clientNo; // Indicate client no
// Construct a thread
public HandleAClient(Socket socket, int clientNo)
connectToClient = socket;
this.clientNo = clientNo;
// Implement the run() method for the thread
public void run()
try
// Create data input and output streams
// DataInputStream isFromClient = new DataInputStream(connectToClient.getInputStream());
// DataOutputStream osToClient = new DataOutputStream(connectToClient.getOutputStream());
     BufferedReader isFromClient = new BufferedReader(new InputStreamReader(connectToClient.getInputStream()));
BufferedWriter osToClient = new BufferedWriter(new OutputStreamWriter(connectToClient.getOutputStream()));
// Continuously serve the client
while (true)
// Receive radius from the client
String radius = "sss";
isFromClient.read();
System.out.println("radius received from client " +
clientNo + ": " + radius);
// Compute area
String area = radius;
// Send area back to the client
osToClient.write(area);
System.out.println("Area found: " + area);
catch(IOException ex)
System.err.println(ex);

Maybe I missed it, but I don't see a osToClient.flush() in the server. Without it the output will just build up.

Tuition.java tutorial program help

I am working on a tutorial program Tuition.java from the Shelly Cashman series Java Programming book. I completed the below code according to instructions, but keep getting these compile errors.
Can anyone tell me where I'm going wrong?
Compile errors:
C:\Documents and Settings\Jay\My Documents\Jays School Papers\CISB 331 Java\Project 3\Tuition.java:94: cannot find symbol
symbol : variable tuition
location: class Tuition
total = tuition + fees;
^
C:\Documents and Settings\Jay\My Documents\Jays School Papers\CISB 331 Java\Project 3\Tuition.java:94: cannot find symbol
symbol : variable fees
location: class Tuition
total = tuition + fees;
^
C:\Documents and Settings\Jay\My Documents\Jays School Papers\CISB 331 Java\Project 3\Tuition.java:94: incompatible types
found : java.lang.String
required: double
total = tuition + fees;
^
3 errors
Tool completed with exit code 1
import java.io.*;
import java.text.DecimalFormat;
public class Tuition
public static void main(String[] args)
//Declare variables
int hours;
double fees, rate, tuition;
displayWelcome();
hours = getHours();
rate = getRate(hours);
tuition = calcTuition(hours, rate);
fees = calcFees(tuition);
displayTotal(tuition + fees);
// start the welcome() method
public static void displayWelcome()
System.out.println("Welcome to the Tuition Calculator program");
System.out.println();
//getHours() will receive the input from the user and use a Try and Catch statement for validation.
public static int getHours()
String strHours;
int hours = 0;
boolean done = false;
BufferedReader dataIn = new BufferedReader(new InputStreamReader(System.in));
while(!done) //Keep asking for integer input while input is in incorrect format.
//get hours from user.
System.out.println("Please enter your total credit hours: ");
strHours = dataIn.readLine();
//Validate input using Try
try
hours = Integer.parseInt(strHours);
done = true;
catch (NumberFormatException e) //Catch error and display response
System.out.println("Your entry was not in the correct format.");
public static double getRate(int hours) //Set hours rate based on amount of hours.
//declare variables
double rate;
if(hours > 15)
rate = hours * 44.50;
else
rate = hours * 50.00;
return rate;
public static double calcTuition(int hours, double rate) //Caclulate tuition and return it.
//declare variables
double tuition;
tuition = hours * rate;
return tuition;
public static double calcFees(double tuition) //Calculate total fees.
//declare variables
double fees;
fees = tuition * .08;
return fees;
public static void displayTotal(double total) //Calculate entire tuition costs and display.
//declare variables
//double total;
total = tuition + fees;
DecimalFormat twoDigits = new DecimalFormat("$#000.00");
System.out.println("Your Tuition is " + total);
Thanks!!

Thanks, I commented out the "total = tuition + fees;
But now I get these compile errors
C:\Documents and Settings\user\Tuition.java:61: missing return statement
^
C:\Documents and Settings\user\Tuition.java:48: unreported exception java.io.IOException; must be caught or declared to be thrown
               strHours = dataIn.readLine();
^
2 errors
Tool completed with exit code 1
Here is the updated code:
{code}import java.io.*;
import java.text.DecimalFormat;
public class Tuition
     public static void main(String[] args)
          //Declare variables
          int hours;
          double fees, rate, tuition;
          displayWelcome();
          hours = getHours();
          rate = getRate(hours);
          tuition = calcTuition(hours, rate);
          fees = calcFees(tuition);
          displayTotal(tuition + fees);
     // start the welcome() method
     public static void displayWelcome()
          System.out.println("Welcome to the Tuition Calculator program");
          System.out.println();
     //getHours() will receive the input from the user and use a Try and Catch statement for validation.
     public static int getHours()
          String strHours;
          int hours = 0;
          boolean done = false;
          BufferedReader dataIn = new BufferedReader(new InputStreamReader(System.in));
          while(!done) //Keep asking for integer input while input is in incorrect format.
               //get hours from user.
               System.out.println("Please enter your total credit hours: ");
               strHours = dataIn.readLine();
               //Validate input using Try
               try
                    hours = Integer.parseInt(strHours);
                    done = true;
               catch (NumberFormatException e) //Catch error and display response
                    System.out.println("Your entry was not in the correct format.");
     public static double getRate(int hours) //Set hours rate based on amount of hours.
          //declare variables
          double rate;
          if(hours > 15)
               rate = hours * 44.50;
          else
               rate = hours * 50.00;
          return rate;
     public static double calcTuition(int hours, double rate) //Caclulate tuition and return it.
          //declare variables
          double tuition;
          tuition = hours * rate;
          return tuition;
     public static double calcFees(double tuition) //Calculate total fees.
          //declare variables
          double fees;
          fees = tuition * .08;
          return fees;
     public static void displayTotal(double total) //Calculate entire tuition costs and display.
          //declare variables
          //double total;
          //total = tuition + fees;
          DecimalFormat twoDigits = new DecimalFormat("$#000.00");
          System.out.println("Your Tuition is " + total);
{code}

Java networking program

Dear Sir,
I amstudying in Deakin International for MIT course and my main subject is java networkprogramming but i feel it diffcuilt.We have diferent assignments so please send me some tutorials or notes based on this subject please also some programming codes also based on each topic as it is hard for me
thankyou

http://java.sun.com/docs/books/tutorial/

Java Network Programming

I am trying to make a Third-party chat client an alternative of rediffbol for rediffchat
* To do this, I downloaded a packet sniffer (Sniphere) and started monitoring the packets sent and received by the original Rediff messenger.*
* Rediff Bol uses the MSNP protocol to connect...*
*1. First the client establishes a tcp connection with the DISPATCH server "203.199.83.62 : 1863"*
*2. then the client sends the DISPATCH server its VERSION and a command so that the dispatch server can send back a list of available notification servers...*
*3. Then the DISPATCH server sends back the client a list of available NOTIFICATION servers......the client connects there and like this it goes on...*
I am using Java. I captured the packet 2. where the command the and the version is sent. I sent the exact packet to the server but due to some reason the dispatch server is not sending back the list of NOTIFICATION servers...
the client.java is attached
there is a difference of negotiation that is occuring between my prog-server and rediffmessenger-server
its like this
pck 1<client-outgoing>: 2<server-incoming> and 3<client-outgoing> which I think is a three way handshaking...its same with my program as the original rediffmessenger
pck 4: this in case of the rediffmessenger is the command and version<outgoing>...same in my case
pck5: this is supposed to be an incoming stream from server 203.199.83.62:1863 which will have the data of available notification servers......WHICH in my case is becoming an outgoing packet from my client<i didnt send anything except the command , refer to client.java> which contains nothing as DATA...and in the later packets the server never sends the list of notification servers...

import java.net.*;
import java.nio.*;
import java.nio.charset.*;
import java.nio.charset.Charset;
import java.io.*;
import java.io.FileOutputStream;
class client extends Object implements java.io.Serializable
private static byte[] getBytes (char[] chars)
Charset cs = Charset.forName ("UTF-8");
CharBuffer cb = CharBuffer.allocate (chars.length);
cb.put (chars);
cb.flip ();
ByteBuffer bb = cs.encode (cb);
return bb.array();
public static void main( String args[] )
File f2=new File("data.dat");
int decimal_value;
char[] extract_char;
extract_char=new char[2];
char[] dat;
byte[] bytes=new byte[19];
byte[] bytes2=new byte[19];
String str;
int count=0;
dat=new char[19];
String getloginserver="564552203134204D534E503820435652300D0A"; //The data packet to ask for notification servers(Hex Dump)
//coverting it into byte array--THIS PART IS WORKING OKAY
for(int i=0;i<(getloginserver.length()-1);i+=2)
extract_char[0]=getloginserver.charAt(i);
extract_char[1]=getloginserver.charAt(i+1);
str=Character.toString(extract_char[0])+Character.toString(extract_char[1]);
decimal_value=Integer.parseInt(str, 16);
dat[count++]=(char)decimal_value;
count=0;
bytes=getBytes(dat);
//for(int j=0;j<30;j++)
//System.out.print((char)bytes[j]);
for(int j=1;j<19;j++)
bytes2[j-1]=bytes[j];
//converting hex dump to byte array completed
// bytes2[] is the byte array which contains the command for the server..it has to be sent...
//establish connection and send
try
Socket toServer;
toServer = new Socket ("65.54.239.80",1863);
OutputStream os = toServer.getOutputStream();
os.write(bytes2);
os.flush();
catch ( IOException e )
System.out.println("Cannot write to the server " + e );
Thats why i didnt post code....its big....

Simple Java Network Programming Question

import java.io.*;
import java.net.*;
public class ConsumerClient
     private static InetAddress host;
     private static final int PORT = 1234;
     private static Socket link;
     private static Resource item;
     private static BufferedReader in;
     private static PrintWriter out;
     private static BufferedReader keyboard;
     public static void main(String[] args)     throws IOException
          try
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               link = new Socket(host, PORT);
               in = new BufferedReader(new InputStreamReader(link.getInputStream()));
               out = new PrintWriter(link.getOutputStream(),true);
               keyboard = new BufferedReader(new InputStreamReader(System.in));
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               do
                    System.out.print("Enter 1 for resource or 0 to quit: ");
                    message = keyboard.readLine();
     if(message.equals("1")**
                         item.takeOne();**
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                    //the socket's output stream...
                    out.println(message);
                    //Accept response from server on
                    //the socket's input stream...
                    response = in.readLine();
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                    System.out.println(response);
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               ioEx.printStackTrace();
          finally
               try
                    if (link!=null)
                         System.out.println("Closing down connection...");
                         link.close();
               catch(IOException ioEx)
                    ioEx.printStackTrace();
}

georgemc wrote:
BlueNo yel-- Auuuuuuuugh!
But the real question is: What is the air-speed velocity of an unladen swallow?

Java Network Programming using UDP protocol

I am trying to send the object using UDP protocol.
In my client class it is giving me NullPointer excetion at clientSocket.send(sendPacket); although sendPacket is not null it has the value that I am passing.
Here is the code :
private boolean clientSrvrComm(AuditorData audData) throws Exception
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I am passing audData through main method.
Any help would be appreciate.
Thanks,
Swati

actually it shouldn't give the null pointer exception and send the object to the server.
I am not able to get, why it is throwing the exception, even there is no class for debugging.

Java network programming explanation

I have refer to following code, i not so understand, can somebody explain it to me? Thanks
try {
e = NetworkInterface.getNetworkInterfaces();
while (e != null && e.hasMoreElements()) {
NetworkInterface net = (NetworkInterface) e.nextElement();
Enumeration enum = net.getInetAddresses();
while (enum.hasMoreElements()) {
InetAddress inet = (InetAddress) enum.nextElement();
new FileServerThread(inet);
catch (SocketException ex) {
}

try {
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    e = NetworkInterface.getNetworkInterfaces();
    // iterate through the Enumeration
    while (e != null && e.hasMoreElements()) {
        // retrieve the next individual NetworkInterface object from
        // the enumeration
        NetworkInterface net = (NetworkInterface) e.nextElement();
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How to write JDBC code in a java thread? for network programming

Hii guys, i am new to java network programming. I developed small swing application for stock controlling in a shop, so i need to run the database in a server. i try the peer to peer scenario, but the response is too late and the application get stuck. there i wl put my data base java class
please help me for this, how can i change this java class to networked JDBC
import com.mysql.jdbc.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
public class ConnectionSet {
private String severIp = "localhost";
private String severPort = "3306";
private String userName = "root";
private String password = "123";
private ResultSet rs;
public void setSeverIp(String Ip) {
severIp = Ip;
public void setSeverPort(String Port) {
severPort = Port;
public void SetUserName(String Name) {
userName = Name;
public void setPassword(String passWord) {
password = passWord;
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Class.forName("com.mysql.jdbc.Driver");
Connection cc = (Connection) DriverManager.getConnection("jdbc:mysql://" + getSeverIp() + ":" + getSeverPort() + "/suriyalanka", getUserName(), getPassword());
Statement s = cc.createStatement();
rs = s.executeQuery(url);
// java.sql.ResultSet rs = (ResultSet) DriverManager.getConnection("jdbc:mysql://"+getSeverIp()+":"+getSeverPort()+"/suriyalanka",getUserName(), getPassword()).createStatement().executeQuery(url);
return rs;
public Connection getConnection() throws Exception {
Class.forName("com.mysql.jdbc.Driver");
Connection cc = (Connection) DriverManager.getConnection("jdbc:mysql://" + getSeverIp() + ":" + getSeverPort() + "/suriyalanka", getUserName(), getPassword());
return cc;
public void setResult(String url) throws Exception {
Class.forName("com.mysql.jdbc.Driver");
Connection cc = (Connection) DriverManager.getConnection("jdbc:mysql://" + getSeverIp() + ":" + getSeverPort() + "/suriyalanka", getUserName(), getPassword());
Statement s = (Statement) cc.createStatement();
s.executeUpdate(url);
public String getSeverIp() {
return severIp;
public String getSeverPort() {
return severPort;
public String getUserName() {
return userName;
public String getPassword() {
return password;
please help me for this, how can i change this java class to networked JDBC
Edited by: 798670 on Sep 29, 2010 6:04 AM

Have you verified that your mysql allows network connections?
In order to allow network connections you have to comment or remove line "skip-networking" in my.ini(windows) or my.cnf(unix) configuration files of your mysql instance.
Or if you have the mysql administrator installed
MySQL Administrator / Startup Variables / Disable networking (uncheck)
By!

Screen has cut out, desperately need help!

The screen on my iMac has cut out. It has happened before and I have had to restart the system to get it back. This time however that hasn't worked. I have booted up the system and can access the files using a second machine via ethernet and the screen did come back briefly when I pressed the ctrl ket before going blank again. I am pretty sure it is not a hardware problem but desperately need a suggestion to help recover the situation.

When I start the machine the screen briefly goes white after the startup chime then goes black again. The same thing happens when I do command-R. The system continues to boot up and I can access the files from my other machine. On two or three ocasions the screen has momentarily come on when I have touched a key or the mouse. For a brief second everything looks OK then it is gone again.

Network Programming exam papers (college exam papers)

hello.
my name is james mcfadden and i am a final year (4th year) undergraduate computing student at Letterkenny Institute of Technology. my e-mail address is [email protected] I have a question here for you. Would you have links to online versions of final year undergraduate Computing exam papers, specifically Networked Applications Development and or Network Management exam papers? I was only able to get access to Trinity College Dublin�s exam papers and Letterkenny IT�s exam papers.
The 2005/06 academic year is the 1st academic year that final year undergraduate computing students at Letterkenny IT are being taught how to continue doing network programming in Java. i was taught how to do simple network programs in Java when I was in 3rd year.
The name of the network programming subject that I�m doing in 4th year is Network Programming for Broadband Systems. It is divided into 2 parts: Programming and Networks. In past exam papers (C++ papers), a student would have had to answer 4 out of 6 questions. There would�ve been 4 programming questions and 2 networking questions on those papers. It is going to be the same for both the Summer and Autumn 2007 Broadband Network Programming exam papers, apart from fact that they will be Java papers and that a lot of the material that I have learned is new.
In 4th year I did Multicast Sockets, Threads, Non-Blocking I/O, Remote Method Invocation, Protocol Handlers, and Content Handlers for the Programming part of the subject (Java Network Programming, 3rd Edition, by Elliote Rusty Harold).
I did Network Security and Network Management for the Networks part of the subject (Computer Networking : A Top-Down Approach Featuring The Internet, 3rd Edition, by James F. Kurose and Keith W. Ross).
Your help is greatly appreciated.
Thank you.

I have a question here for you.
Would you have links to online versions of final year
undergraduate Computing exam papers, specifically
Networked Applications Development and or Network
Management exam papers? No

Desperately need Java network programming help!!!

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