A Socket Program Java

Hello Dear Java Forums Team I'am Alfonso Franco who is reporting my socket program
as http://www.javaworld.com without a port number assigned only the Input of www.javaworld.com more the following Code: System.out.printIn( " Enter a Host Name: ", + name) ;
System.out.printIn( " Enter pin code number device: " + device) ;
System.out.printIn( " Ours server is detecting a successfull connection " ) ;
System.out.printIn( " Ours server sorry detect error didn't match name and number ") ;
Please I'am looking for someone who will help me with my question is really this socket program works correctly if not give more reference to do it's improved . Thank you Team
Alfonso Franco
[email protected]

Remove "if (input.ready())". readLine() will block, consuming zero cpu, until it gets data, EOF or an IOException.
I've been programming sockets since mid-80's and I've never used something like socket.ready(). The normal way to do sockets is either to read() / readLine() or to select() / poll(). ready(), available() and such should come with big blinking warning labels.

Similar Messages

Socket programming + java.security.AccessControlException: access denied

the code below is for a particular port and IP ..what is the command for granting permission for all the sites?
please help, i have been unable to tackle this problem from the past 24 hours.
iam getting an error too..
java.security.AccessControlException: access denied (java.net.SocketPermission yahoo.com resolve)
grant {
permission java.net.SocketPermission
"puffin.eng.sun.com:7777",
"connect, accept";

..

Asynchronous socket programming in Java?

I am a C++ programmer, I just wonder how do I do asynchronous programming in Java?
In VC++, you can hook an event handler to the socket and the system will fire an event whenever there is data coming in to the socket. The event handler can then spawn a thread and handle the network message.
In Unix, you can use the select() function. This function will return whenever the indicated socket fires events. If nothing happens within the timeout period, the function simply returns.
What about in Java? I don't see any methods that allows you to hook an event handler to it. Is there anything like select() function in Unix?
Thanks so much.

There is something very much like C's select: selectors. I don't immediately know where to read more about them but google for things like "java selector example", "java nio tutorial", etc (NIO = new I/O, the library where selectors live.)
Another way to do async sockets in Java is by threading. That is the traditional way before New I/O. It's still a perfectly good and easy way, thanks to Java's easy threading. Downside is that it scales to only maybe 100-200 simultaneous connections per server (will depend on your operating system). For thread-based sockets check Sun's Java socket tutorial (first item when you google "java socket tutorial").

File transfer, read write through sockets in client server programming java

Hello All, need help again.
I am trying to create a Client server program, where, the Client first sends a file to Server, on accepting the file, the server generates another file(probably xml), send it to the client as a response, the client read the response xml, parse it and display some data. now I am successful sending the file to the server, but could not figure out how the server can create and send a xml file and send it to the client as response, please help. below are my codes for client and server
Client side
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class XMLSocketC
     public static void main(String[] args) throws IOException
          //Establish a connection to socket
          Socket toServer = null;
          String host = "127.0.0.1";
          int port = 4444;
          try
               toServer = new Socket(host, port);
               } catch (UnknownHostException e) {
            System.err.println("Don't know about host: localhost.");
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for the connection to host.");
            System.exit(1);
          //Send file over Socket
        //===========================================================
        BufferedInputStream fileIn = null;
          BufferedOutputStream out = null;
          // File to be send over the socket.
          File file = new File("c:/xampp/htdocs/thesis/sensorList.php");
          // Checking for the file to be sent.
          if (!file.exists())
               System.out.println("File doesn't exist");
               System.exit(0);
          try
               // InputStream to read the file
               fileIn = new BufferedInputStream(new FileInputStream(file));
          }catch(IOException eee)
               System.out.println("Problem, kunne ikke lage fil");
          try
               InetAddress adressen = InetAddress.getByName(host);
               try
                    System.out.println("Establishing Socket Connection");
                    // Opening Socket
                    Socket s = new Socket(adressen, port);
                    System.out.println("Socket is clear and available.....");
                    // OutputStream to socket
                    out = new BufferedOutputStream(s.getOutputStream());
                    byte[] buffer = new byte[1024];
                    int numRead;
                    //Checking if bytes available to read to the buffer.
                    while( (numRead = fileIn.read(buffer)) >= 0)
                         // Writes bytes to Output Stream from 0 to total number of bytes
                         out.write(buffer, 0, numRead);
                    // Flush - send file
                    out.flush();
                    // close OutputStream
                    out.close();
                    // close InputStrean
                    fileIn.close();
               }catch (IOException e)
          }catch(UnknownHostException e)
               System.err.println(e);
        //===========================================================
        //Retrieve data from Socket.
          //BufferedReader in = new BufferedReader(new InputStreamReader(toServer.getInputStream()));
          DataInputStream in = new DataInputStream(new BufferedInputStream(toServer.getInputStream()));
          //String fromServer;
        //Read from the server and prints.
          //Receive text from server
          FileWriter fr = null;
          String frn = "xxx_response.xml";
          try {
               fr = new FileWriter(frn);
          } catch (IOException e1) {
               // TODO Auto-generated catch block
               e1.printStackTrace();
          try{
               String line = in.readUTF();                    //.readLine();
               System.out.println("Text received :" + line);
               fr.write(line);
          } catch (IOException e){
               System.out.println("Read failed");
               System.exit(1);
        in.close();
        toServer.close();
public class XMLSocketS
      public static void main(String[] args) throws IOException
          //Establish a connection to socket
           ServerSocket serverSocket = null;
             try {
                 serverSocket = new ServerSocket(4444);
             } catch (IOException e) {
                 System.err.println("Could not listen on port: 4444.");
                 System.exit(1);
          Socket clientLink = null;
          while (true)
                    try
                         clientLink = serverSocket.accept();
                       System.out.println("Server accepts");
                         BufferedInputStream inn = new BufferedInputStream(clientLink.getInputStream());
                         BufferedOutputStream ut = new BufferedOutputStream(new FileOutputStream(new File("c:/xampp/htdocs/received_from_client.txt")));
                         byte[] buff = new byte[1024];
                         int readMe;
                         while( (readMe = inn.read(buff)) >= 0)
                         {     //reads from input stream, writes the file to disk
                              ut.write(buff, 0, readMe);
                         // close the link to client
                         clientLink.close();
                         // close InputStream
                         inn.close();
                         // flush
                         ut.flush();
                         // close OutputStream
                         ut.close();
                         //Sending response to client
                         //============================================================
                         //============================================================
                         System.out.println("File received");
          }catch(IOException ex)
          {System.out.println("Exception.");}
                    finally
                         try
                              if (clientLink != null) clientLink.close();
                         }catch(IOException e) {}
             clientLink.close();
             //serverSocket.close();
}

SERVER
import java.net.*;
import java.io.*;
public class XMLSocketS
      public static void main(String[] args) throws IOException
               //Establish a connection to socket
           ServerSocket serverSocket = null;
             try {
                 serverSocket = new ServerSocket(4545);
             } catch (IOException e) {
                 System.err.println("Could not listen on port: 4444.");
                 System.exit(1);
          Socket clientLink = null;
              try
                         clientLink = serverSocket.accept();
                     System.out.println("Server accepts the client request.....");
                     BufferedInputStream inn = new BufferedInputStream(clientLink.getInputStream());
                         BufferedOutputStream ut = new BufferedOutputStream(new FileOutputStream(new File("c:/xampp/htdocs/received_from_client.txt")));
                         byte[] buff = new byte[1024];
                         int readMe;
                         while( (readMe = inn.read(buff)) >= 0)
                         {     //reads from input stream, writes the file to disk
                              ut.write(buff, 0, readMe);
                         ut.flush();
                         //Sending response to client
                         //============================================================
                         BufferedInputStream ftoC = null;
                         BufferedOutputStream outtoC = null;
                         // File to be send over the socket.
                         File file = new File("c:/xampp/htdocs/thesis/user_registration_response.xml");
                         try
                              // InputStream to read the file
                               ftoC = new BufferedInputStream(new FileInputStream(file));
                         }catch(IOException eee)
                         {System.out.println("Problem reading file");}
                         // OutputStream to socket
                         outtoC = new BufferedOutputStream(clientLink.getOutputStream());
                         byte[] buffer = new byte[1024];
                         int noRead;
                         //Checking if bytes available to read to the buffer.
                         while( (noRead = ftoC.read(buffer)) >= 0)
                              // Writes bytes to Output Stream from 0 to total number of bytes
                              outtoC.write(buffer, 0, noRead);
                         outtoC.flush();
                         //============================================================
                         System.out.println("File received");
          }catch(IOException ex)
          {System.out.println("Exception.");}
                    finally
                         try
                              if (clientLink != null) clientLink.close();
                         }catch(IOException e) {}
             clientLink.close();
             //serverSocket.close();
      }CLIENT SIDE
import java.io.*;
import java.net.*;
public class XMLSocketC
          @SuppressWarnings("deprecation")
          public static void main(String[] args)
               // Server: "localhost" here. And port to connect is 4545.
               String host = "127.0.0.1";
               int port = 4545;
               BufferedInputStream fileIn = null;
               BufferedOutputStream out = null;
               // File to be send over the socket.
               File file = new File("c:/xampp/htdocs/thesis/sensorList.xml");
               try
                    // InputStream to read the file
                    fileIn = new BufferedInputStream(new FileInputStream(file));
               }catch(IOException eee)
               {System.out.println("Problem");}
               try
                         System.out.println("Establishing Socket Connection");
                         // Opening Socket
                         Socket clientSocket = new Socket(host, port);
                         System.out.println("Socket is clear and available.....");
                         // OutputStream to socket
                         out = new BufferedOutputStream(clientSocket.getOutputStream());
                         byte[] buffer = new byte[1024];
                         int numRead;
                         //Checking if bytes available to read to the buffer.
                         while( (numRead = fileIn.read(buffer)) >= 0)
                              // Writes bytes to Output Stream from 0 to total number of bytes
                              out.write(buffer, 0, numRead);
                         // Flush - send file
                         out.flush();
                         //=======================================
                         DataInputStream in = new DataInputStream(new BufferedInputStream(clientSocket.getInputStream()));
                         BufferedWriter outf = new BufferedWriter(new FileWriter("c:/xampp/htdocs/received_from_server.txt",true));
                         String str;
                         while(!(str = in.readLine()).equals("EOF")) {
                              System.out.println("client : Read line -> <" + str + ">");
                              outf.write(str);//Write out a string to the file
                              outf.newLine();//write a new line to the file (for better format)
                              outf.flush();
                         //=======================================
                         // close OutputStream
                         out.close();
                         // close InputStrean
                         fileIn.close();
                         // close Socket
                         clientSocket.close();
                    }catch (IOException e)
                    {System.out.println("Exception.");}
     Could you please point where am I doing the stupid mistake, client to server is working properly, but the opposite direction is not.
Thanks

How to control tcp connection with java tcp socket programing ??

Hi,
I am connecting a server as using java socket programming.
When server close the connection (socket object) as using close() method ,
I can not detect this and My program continue sending data as if there is a connection with server.
How to catch the closing connection ( socket ) with java socket programming.
My Client program is as following :
import java.io.PrintWriter;
import java.net.Socket;
public class client
public client()
   * @param args
public static void main(String[] args)
    Socket socket=null;
    PrintWriter pw=null;
    try
                      socket = new Socket("localhost",5555);
                      pw = new PrintWriter(socket.getOutputStream(),true);
                      int i=0;
                      while (true)
                        i++;
                        pw.println(i+". message is being send.");
                        Thread.sleep(5000);
    } catch (Exception ex)
                      ex.printStackTrace();
    } finally
                      try
                        if(pw!=null)pw.close();
                        if(socket!=null)socket.close();
                      } catch (Exception ex)
                        ex.printStackTrace();
                      } finally
}

I changed the code as following. But I couldn't catch the EOFException when I read from the socket. How can I catch this exception ?
import java.io.BufferedReader;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
public class client
public client()
   * @param args
public static void main(String[] args)
    Socket socket=null;
    PrintWriter pw=null;
    BufferedReader bufIn=null;
    InputStreamReader inRead=null;
    InputStream in=null;
    try
                      socket = new Socket("localhost",5555);
                      in = socket.getInputStream();
                      inRead = new InputStreamReader(in);
                      bufIn = new BufferedReader(inRead);
                      pw = new PrintWriter(socket.getOutputStream(),true);
                      int i=0;
                      while (true)
                        i++;
                        try
                          bufIn.readLine();
                          pw.println(i+". message is being send.");
                          System.out.println(i+". message has been send");
                        } catch (Exception ex2)
                          System.out.println(ex2.toString());
                          System.out.println(i+". message could not be send");
                        } finally
                        Thread.sleep(5000);
    } catch (EOFException ex)
                      ex.printStackTrace();
    } catch (InterruptedException ex)
                      ex.printStackTrace();
    } catch (IOException ex)
                      ex.printStackTrace();
    } finally
                      try
                        if(pw!=null)pw.close();
                        if(socket!=null)socket.close();
                      } catch (Exception ex)
                        ex.printStackTrace();
                      } finally
}

Raw socket programming is avilable in java

hello,
I want to reset my target device using device
MAC address (not IP address).
Is java support raw socket programming.
can i send packets using MAC address in Java like C.
I search in google. but, it shows there is no raw socket pgm support in java.
any one help me this issue.

JPCap

Java Swing and Socket Programming

I am making a Messenger like yahoo Messenger using Swing and Socket Programming ,Multithreading .
Is this techology feasible or i should try something else.
I want to display my messenger icon on task bar as it comes when i install and run Yahoo Messenger.
Which class i should use.

I don't really have an answer to what you are asking. But I am developing the same kind of application. I am using RMI for client-server and server-server (i have distributed servers) communication and TCP/IP for client-client. So may be we might be able to help each other out. My email id is [email protected]
Are you opening a new socket for every conversation? I was wondering how to multithread a socket to reuse it for different connections, if it is possible at all.
--Poonam.

File descriptor leak in socket programming

We have a complex socket programming client package in java using java.nio (Selectors, Selectable channel).
We use the package to connect to a server.
Whenever the server is down, it tries to reconnect to the server again at regular intervals.
In that case, the number of open file descriptors build up with each try. I am able to cofirm this using "pfile <pid>" command.
But, it looks like we are closing the channels, selectors and the sockets properly when it fails to connect to the server.
So we are unable to find the coding that causes the issue.
We run this program in solaris.
Is there a tool to track down the code that leaks the file descriptor.
Thanks.

Don't close the selector. There is a selector leak. Just close the socket channel. As this is a client you should then also call selector.selctNow() to have the close take final effect. Otherwise there is also a socket leak.

Socket programming usin nio package

hello frens i m new to socket programming
i come to know that nio packaage provides more sophisticated and efficient API to deal with socket programming issue
I need to know where i can get tutorial about socket programming using nio pacakage

Try google
http://www.google.co.uk/search?q=java+nio+tutorial

[Urgent]3G Socket programming

May I use socket for 3G networks?
I use the demo provided by the WTK2.5-Beta(NetworkDemo), it works well in the simulator. However, when I download the program to the mobile phone, it seems that the mobile phone that runs ServerSocket cannot create the socket ... all the 2 handsets use a 3G SIM card provided by a Hong Kong ISP smartTone ... What can I do?
Please help~ provide any web page of codes, thanks very much!

1.     We want to create a socket connection which can
remain open and live for ever till it is closed. Is
this possible in java socket programming?Yes, but it isn't practical in the real networking world. So your code had better be prepared to deal with network failures.
2.     I am just wondering in order to communicate with
the third party over the socket connection, does this
other party requires to run something specific on
their end? I am not able to understand how will my
java code communicate with their server otherwise.It has nothing to do with java. Sockets send and recieve messages. The applications at either end, regardless of the language that they are written in, must handle those messages.
3.     Can we send and receive data over the socket
created and also is their specific format for the
data? Yes.
Can we send files of data over this connection?Yes. (Although I don't know why you would need to do that if you are doing credit card auths.)
It would be great if someone can comment on these
questions and also if possible please provide some
code that can create socket connection.The tutorial.....
http://java.sun.com/docs/books/tutorial/networking/sockets/index.html

RESTFUL Web Services vs Socket Programming Performance

Hi guys,
I will have an application which will have a service serving about to 30 million users/day and a mean of 5 requests/user.
It means that there will be about 150 million requests per day. I will have two servers behind a load balancer and my clients will be both Java and C++.
I think to implement RESTFUL Web Services but afraid of performance issues.
Did you have a knowledge about the performances of web service and socket programming in such a high loaded project?
Tnx.
Ayberk

ayberkcansever wrote:
Hi guys,
I will have an application which will have a service serving about to 30 million users/day and a mean of 5 requests/user.
It means that there will be about 150 million requests per day. I will have two servers behind a load balancer and my clients will be both Java and C++.
I think to implement RESTFUL Web Services but afraid of performance issues.
Did you have a knowledge about the performances of web service and socket programming in such a high loaded project?It depends on the CPUs, RAM, disks, and network configurations of those servers.
It depends on how the requests are distributed throughout the day.
It depends on how big the requests are and how big the responses are.

First Very Simple Socket Program

Hello,
I am learning about Sockets and ServerSockets and how I can use the. I am trying to make the simplest server/client program possible just for my understanding before I go deper into it. I have written two programs. theserver.java and theclient.java the sere code looks like this....
import java.net.*;
import java.io.*;
import java.util.*;
public class theserver
public static void main(String[] args)
{   // IOReader r = new IOReader();
        int prt = 3333;
        BufferedReader in;
         PrintWriter out;
        ServerSocket serverSocket;
        Socket clientSocket = null;
try{
serverSocket = new ServerSocket(prt); // creates the socket looking on prt (3333)
System.out.println("The Server is now running...");
while(true)
    clientSocket = serverSocket.accept(); // accepts the connenction
    clientSocket.getKeepAlive(); // keeps the connection alive
    out = new PrintWriter(clientSocket.getOutputStream(),true);
    in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
     if(in.ready())
     System.out.println(in.readLine()); // print it
catch (IOException e) {
    System.out.println("Accept failed:"+prt);
}and the client looks like this
import java.net.*;
import java.io.*;
public class theclient
public static void main(String[] args)
    BufferedReader in;
    PrintWriter out;
    IOReader r = new IOReader();
    PrintWriter sender;
    Socket sock;
try{
    sock = new Socket("linuxcomp",3333); // creates a new connection with the server.
    sock.setKeepAlive(true); // keeps the connection alive
    System.out.println("Socket is connected"); // confirms socket is connected.
    System.out.println("Please enter a String");
     String bob = r.readS();
      out = new PrintWriter(sock.getOutputStream(),true);
    out.print(bob); // write bob to the server
catch(IOException e)
       System.out.println("The socket is now disconnected..");
}If you notice in the code I use a class I made called IOReader. All that class is, is a buffered reader for my System.in. (just makes it easier for me)
Ok now for my question:
When I run this program I run the server first then the client. I type "hello" into my system.in but on my server side, it prints "null" I can't figure out what I am doing wrong, if I am not converting correctly, or if the message is not ever being sent. I tried putting a while(in.read()) { System.out.println("whatever") } it never reaches a point where in.ready() == true. Kinda of agrivating. Because I am very new to sockets, I wanna aks if there is somthing wrong with my code, or if I am going about this process completely wrong. Thank you to how ever helps me,
Cobbweb

An example of Creating a Client Socket (Java socket programming tutorial)
try {
        InetAddress addr = InetAddress.getByName("hotdir.biz");
        int port = 80;
        // This constructor will block until the connection succeeds
        Socket socket = new Socket(addr, port);
    } catch (UnknownHostException e) {
    } catch (IOException e) {
    // Create a socket with a timeout
    try {
        InetAddress addr = InetAddress.getByName("hotdir.biz");
        int port = 80;
        SocketAddress sockaddr = new InetSocketAddress(addr, port);
        // Create an unbound socket
        Socket sock = new Socket();
        // This method will block no more than timeoutMs.
        // If the timeout occurs, SocketTimeoutException is thrown.
        int timeoutMs = 2000;   // 2 seconds
        sock.connect(sockaddr, timeoutMs);
    } catch (UnknownHostException e) {
    } catch (SocketTimeoutException e) {
    } catch (IOException e) {
    }See socket tutorial here http://www.developerzone.biz/index.php?option=com_content&task=view&id=94&Itemid=36

Socket Programming-Not getting response from server.

Hi,
I am trying to communicate with server using java socket programming, I am getting the response for first two times third time when I am trying to write some thing I am not getting any response from the server,
I am writing to migrate the vb code to Java the vb is using a c++ dll to communicate with the server and we tried accessing the dll from java using JNI then it is working fine, this dll is dependent on windows so we want to avoid the dependency with windows that is why we are going for socket programming, Please help on this.

Hi,
I am writing the data in forms of string
like
Socket sockt = new Socket(ipAddress, portNo);
out= new DataOutputStream(sockt.getOutputStream());
in = new DataInputStream(sockt.getInputStream());
out.writeBytes("Serv");
out.writeBytes("Serv,32");
out.writeBytes("home,serv32,run.prg,sucess");
these are the strings to communicate with server.
I am trying to read the same
StringBuffer buf = new StringBuffer();
          byte b = '\0';
                    try {
               while ((b = in.readByte()) != '\0')
                    char ch = (char) b;
                    buf.append(ch);
          } catch (Exception e) {
               System.out.println(e.getStackTrace());
we are getting the response for the first two strings, but for the third string it is getting stucked for some time and returing some junk values like '???' we are sending the same string using JNI and it is working.

Simple Socket Programming, But,.......

This code is Server, Client Socket program code.
Client send data to server and then, Server get data and save it
to file in server.
I think client works well.
But, Server.java file have some problem.
It generate ClassNotFoundException!
So the result file have garbage value only.
Any idea please................
/////////////////////////// Server.java /////////////////////////////////
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Server extends JFrame
     private JTextField enter;
     private JTextArea display;
     ObjectInputStream input;
     ObjectOutputStream output;
     FileOutputStream resultFile;
     public Server(){
          super("Server");
          Container c = getContentPane();
          enter = new JTextField();
          enter.setEnabled(false);
          enter.addActionListener(
               new ActionListener(){
                    public void actionPerformed(ActionEvent ev){
                         //None
          c.add(enter, BorderLayout.NORTH);
          display = new JTextArea();
          c.add(new JScrollPane(display),
               BorderLayout.CENTER);
          setSize(300, 150);
          show();
     public void runServer(){
          ServerSocket server;
          Socket connection;
          int counter = 1;
          display.setText("");
          try{
               server = new ServerSocket(8800, 100);
               while(true){
                    display.append("Waiting for connection\n" + counter);
                    connection = server.accept();
                    display.append("Connection " + counter +
                         "received from: " + connection.getInetAddress().getHostName());
                    resultFile = new FileOutputStream("hi.txt");
                    output = new ObjectOutputStream(resultFile);
                    output.flush();
                    input = new ObjectInputStream(
                         connection.getInputStream()
                    display.append("\nGod I/O stream, I/O is opened\n");
                    enter.setEnabled(true);
                    DataForm01 data = null;
                    try{
                         data = (DataForm01) input.readObject();
                         output.writeObject(data);
                         data = (DataForm01) input.readObject();
                         output.writeObject(data);
                    catch(NullPointerException e){
                         display.append("Null pointer Exception");
                    catch(ClassNotFoundException cnfex){
                         display.append("\nUnknown Object type received");
                    catch(IOException e){
                         display.append("\nIOException Occured!");
                    if(resultFile != null){
                         resultFile.flush();
                         resultFile.close();
                    display.append("\nUser Terminate connection");
                    enter.setEnabled(false);
                    input.close();
                    output.close();
                    connection.close();
                    ++counter;
          catch(EOFException eof){
               System.out.println("Client Terminate Connection");
          catch(IOException io){
               io.printStackTrace();
          display.append("File is created!");
     public static void main(String[] args){
          Server app = new Server();
          app.addWindowListener(
               new WindowAdapter(){
                    public void windowClosing(WindowEvent e){
                         System.exit(0);
          app.runServer();
/////////////////////////// client.java /////////////////////////////////
* Client.java
* @author Created by Omnicore CodeGuide
package Client;
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Client extends JFrame
     private JTextField enter;
     private JTextArea display;
     ObjectOutputStream output;
     String message = "";
     //DataForm01 dfrm[];
     public Client(){
          super("Client");
          Container c = getContentPane();
          enter = new JTextField();
          enter.setEnabled(false);
          enter.addActionListener(
               new ActionListener(){
                    public void actionPerformed(ActionEvent e){
                         //None.
          c.add(enter, BorderLayout.NORTH);
          display = new JTextArea();
          c.add(new JScrollPane(display), BorderLayout.CENTER);
          setSize(300, 150);
          show();
     public void runClient(){
          Socket client;
          try{
               display.setText("Attemption Connection...\n");
               client = new Socket(InetAddress.getByName("127.0.0.1"), 8800);
               display.append("Connected to : = " +
                    client.getInetAddress().getHostName());
               output = new ObjectOutputStream(
                    client.getOutputStream()
               output.flush();
               display.append("\nGot I/O Stream, Stream is opened!\n");
               enter.setEnabled(true);
               dfrm = new DataForm01[10];
               for(int i=0; i<10; i++){
                    dfrm[i] = new DataForm01();
                    dfrm.stn = i;
                    dfrm[i].name = "Jinbom" + Integer.toString(i);
                    dfrm[i].hobby = "Soccer" + Integer.toString(i);
                    dfrm[i].point = (double)i;
               for(int i=0; i<10; i++){
                    try{
                         output.writeObject(dfrm[i]);
                         display.append(dfrm[i].getData());
                    catch(IOException ev){
                         display.append("\nClass is not founded!\n");
               DataForm01 dfrm = new DataForm01();
               dfrm.stn=1;
               dfrm.name="Jinbom";
               dfrm.hobby = "Soccer";
               dfrm.point = (double)0.23;
               DataForm01 dfrm02 = new DataForm01();
               dfrm02.stn = 1;
               dfrm02.name = "Jimbin";
               dfrm02.hobby = "Soccer";
               dfrm02.point = 0.4353;
               try{
                    output.writeObject(dfrm);
                    display.append(dfrm.getData());
                    output.writeObject(dfrm02);
                    display.append(dfrm.getData());
               catch(IOException ev){
                    display.append("\nClass is not founded!\n");
               if(output != null) output.flush();
               display.append("Closing connection.\n");
               output.close();
               client.close();
          catch(IOException ioe){
               ioe.printStackTrace();
     public static void main(String[] args){
          Client app = new Client();
          app.addWindowListener(
               new WindowAdapter(){
                    public void windowClosing(WindowEvent e){
                         System.exit(0);
          app.runClient();
/////////////////////////// DataForm01.java /////////////////////////////////
import java.io.*;
public class DataForm01 implements Serializable
     int stn;
     String name;
     String hobby;
     double point;
     public String getData(){
          return Integer.toString(stn) + name + hobby + Double.toString(point);

This is indented code. ^^;
It's better to view.
////////////////////////// Server.java /////////////////////////////////////////
* Server.java
* @author Created by Omnicore CodeGuide
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Server extends JFrame
     private JTextField enter;
     private JTextArea display;
     ObjectInputStream input;
     ObjectOutputStream output;
     FileOutputStream resultFile;
     public Server(){
          super("Server");
          Container c = getContentPane();
          enter = new JTextField();
          enter.setEnabled(false);
          enter.addActionListener(
               new ActionListener(){
                    public void actionPerformed(ActionEvent ev){
                         //None
          c.add(enter, BorderLayout.NORTH);
          display = new JTextArea();
          c.add(new JScrollPane(display),
                 BorderLayout.CENTER);
          setSize(300, 150);
          show();
     public void runServer(){
          ServerSocket server;
          Socket connection;
          int counter = 1;
          display.setText("");
          try{
               server = new ServerSocket(8800, 100);
               while(true){
                    display.append("Waiting for connection\n" + counter);
                    connection = server.accept();
                    display.append("Connection " + counter +
                         "received from: " + connection.getInetAddress().getHostName());
                    resultFile = new FileOutputStream("hi.txt");
                    output = new ObjectOutputStream(resultFile);
                    output.flush();
                    input = new ObjectInputStream(
                         connection.getInputStream()
                    display.append("\nGod I/O stream, I/O is opened\n");
                    enter.setEnabled(true);
                    DataForm01 data = null;
                    for(int i=0; i<10; i++){
                         try{
                              data = (DataForm01) input.readObject();
                              if(data == null) break;
                              output.writeObject(data);
                         catch(NullPointerException e){
                              display.append("Null pointer Exception");
                         catch(ClassNotFoundException cnfex){
                              display.append("\nUnknown Object type received");
                         catch(IOException e){
                              display.append("\nIOException Occured!");
                    DataForm01 data = null;
                    try{
                         data = (DataForm01) input.readObject();
                         output.writeObject(data);
                         data = (DataForm01) input.readObject();
                         output.writeObject(data);
                    catch(NullPointerException e){
                         display.append("Null pointer Exception");
                    catch(ClassNotFoundException cnfex){
                         display.append("\nUnknown Object type received");
                    catch(IOException e){
                         display.append("\nIOException Occured!");
                    if(resultFile != null){
                         resultFile.flush();
                         resultFile.close();
                    display.append("\nUser Terminate connection");
                    enter.setEnabled(false);
                    input.close();
                    output.close();
                    connection.close();
                    ++counter;
          catch(EOFException eof){
               System.out.println("Client Terminate Connection");
          catch(IOException io){
               io.printStackTrace();
          display.append("File is created!");
     public static void main(String[] args){
          Server app = new Server();
          app.addWindowListener(
               new WindowAdapter(){
                    public void windowClosing(WindowEvent e){
                         System.exit(0);
          app.runServer();
////////////////////////// Client.java /////////////////////////////////////////
* Client.java
* @author Created by Omnicore CodeGuide
package Client;
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Client extends JFrame
     private JTextField enter;
     private JTextArea display;
     ObjectOutputStream output;
     String message = "";
     //DataForm01 dfrm[];
     public Client(){
          super("Client");
          Container c = getContentPane();
          enter = new JTextField();
          enter.setEnabled(false);
          enter.addActionListener(
               new ActionListener(){
                    public void actionPerformed(ActionEvent e){
                         //None.
          c.add(enter, BorderLayout.NORTH);
          display = new JTextArea();
          c.add(new JScrollPane(display), BorderLayout.CENTER);
          setSize(300, 150);
          show();
     public void runClient(){
          Socket client;
          try{
               display.setText("Attemption Connection...\n");
               client = new Socket(InetAddress.getByName("127.0.0.1"), 8800);
               display.append("Connected to : = " +
                      client.getInetAddress().getHostName());
               output = new ObjectOutputStream(
                    client.getOutputStream()
               output.flush();
               display.append("\nGot I/O Stream, Stream is opened!\n");
               enter.setEnabled(true);
               dfrm = new DataForm01[10];
               for(int i=0; i<10; i++){
                    dfrm[i] = new DataForm01();
                    dfrm.stn = i;
                    dfrm[i].name = "Jinbom" + Integer.toString(i);
                    dfrm[i].hobby = "Soccer" + Integer.toString(i);
                    dfrm[i].point = (double)i;
               for(int i=0; i<10; i++){
                    try{
                         output.writeObject(dfrm[i]);
                         display.append(dfrm[i].getData());
                    catch(IOException ev){
                         display.append("\nClass is not founded!\n");
               DataForm01 dfrm = new DataForm01();
               dfrm.stn=1;
               dfrm.name="Jinbom";
               dfrm.hobby = "Soccer";
               dfrm.point = (double)0.23;
               DataForm01 dfrm02 = new DataForm01();
               dfrm02.stn = 1;
               dfrm02.name = "Jimbin";
               dfrm02.hobby = "Soccer";
               dfrm02.point = 0.4353;
               try{
                    output.writeObject(dfrm);
                    display.append(dfrm.getData());
                    output.writeObject(dfrm02);
                    display.append(dfrm.getData());
               catch(IOException ev){
                    display.append("\nClass is not founded!\n");
               if(output != null) output.flush();
               display.append("Closing connection.\n");
               output.close();
               client.close();
          catch(IOException ioe){
               ioe.printStackTrace();
     public static void main(String[] args){
          Client app = new Client();
          app.addWindowListener(
               new WindowAdapter(){
                    public void windowClosing(WindowEvent e){
                         System.exit(0);
          app.runClient();
////////////////////////// DataForm01.java /////////////////////////////////////////
* DataForm01.java
* @author Created by Omnicore CodeGuide
import java.io.*;
public class DataForm01 implements Serializable
     int stn;
     String name;
     String hobby;
     double point;
     public String getData(){
          return Integer.toString(stn) + name + hobby + Double.toString(point);

Transfering a file through Socket programming

Hi all,
I want to return a file from server to client through a socket. I tried using ObjectOutput Stream where in I returned a java.io.File from server. But at client side when I say file.getLeangth() it comes as 0 and if I try to assign FileInputStream on the object it throws an exception as the file not found as the path associated with the file will be of Server.
So can anyone help as to how to transfer a file through socket programming???
thx in advance
MK

java.io.File is NOT the contents of the file. It really just represents the path.
If you want to transfer the file's contents, you'll have to use a FileInputStream or FileReader, read from it, and then write the bytes or chars on the wire.

A Socket Program Java

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