Client-Server programming with Sockets

How to read user input from GUI in client socket and send the data to server socket? Can someone give example of the coding?
Thank you.

Take a look at reply 28 of Program hanging on a Thread. That post is a swing based socket client. If you are using Swing you must ensure that all swing activity occurs on the AWT Event Dispatch Thread. That's the reason for the use of invokeLater.
Reply 21 on the same thread is a multithreaded command line server.

Similar Messages

Client/Server Program with GUI

Hello all...I've been working on an instant messenger type of program, and need a way to keep track of different clients using my server, and then posting that list to my clients' GUI, to show them who is "Online" Also, I am having trouble, letting my server know which client to send a message to...i.e. client1 tries to say "Hello" to client2 but nothing happens... Anyways I gonna keep pluggin away at it but if you have any insight let me know please...Damn I just got this new error a second ago, for no apperent reason...
ReceivingThread.java [156:1] cannot resolve symbol
symbol : constructor SendingThread (int)
location: class SendingThread
SendingThread sendingThread = new SendingThread(8205);
^
1 error
...and here's the code for it, just popped up outta nowhere...thx again!!
import java.io.*;
import java.net.*;
import java.util.StringTokenizer;
public class ReceivingThread extends Thread {
private byte[] message;
private int portNumber;
private InetAddress address;
private BufferedReader input;
private boolean keepListening = true;
// ReceivingThread constructor
public ReceivingThread( Socket clientSocket )
// invoke superclass constructor to name Thread
super( "ReceivingThread: " + clientSocket );
// set timeout for reading from clientSocket and create
// BufferedReader for reading incoming messages
try {
clientSocket.setSoTimeout( 5000 );
input = new BufferedReader( new InputStreamReader(
clientSocket.getInputStream() ) );
// handle exception creating BufferedReader
catch ( IOException ioException ) {
ioException.printStackTrace();
} // end ReceivingThread constructor
// listen for new messages and deliver them to MessageListener
public void run()
String message;
// listen for messages until stoppped
while ( keepListening ) {
// read message from BufferedReader
try {
message = input.readLine();
// handle exception if read times out
catch ( InterruptedIOException interruptedIOException ) {
// continue to next iteration to keep listening
continue;
// handle exception reading message
catch ( IOException ioException ) {
ioException.printStackTrace();
break;
// ensure non-null message
if ( message != null ) {
// tokenize message to retrieve user name
// and message body
StringTokenizer tokenizer = new StringTokenizer( message, "|" );
// ignore messages that do not contain a user
// name and message body
if ( tokenizer.countTokens() == 2 ) {
// send message to the client through SendingThread; fill in proper info
SendingThread sendingThread = new SendingThread(8205);
sendingThread.start();
else
// if disconnect message received, stop listening
if ( message.equalsIgnoreCase("DISCONNECT") ) {
keepListening = false;
} // end if
} // end while
// close BufferedReader (also closes Socket)
try {
input.close();
// handle exception closing BufferedReader
catch ( IOException ioException ) {
ioException.printStackTrace();
} // end method run
}

1) The error is down to the fact that you don't have a constructor declared for class SendingThread that accepts an int.
2) To show who's on line use a static ArrayList at the server side. Everytime a user connects, just do:
String user = "bob";
arrayList.add(user);
ArrayList is serialisable so you can serialise the object and send it over the network to the client. The client can deserialise the object and it will in effect have a copy of the object.
When the client wants to display the names you just need to iterate over the array list.
As new users connect you will have to update the list and also inform all other connected users that a new user has connected. You could do this by either pushing the data (client waits for data and server sends it immediately) or pulling the data at regular time intervals. I would suggest the first method as you will (or should) already have a thread set up to listen for incoming data.
3) For sending messages between two hosts, you might want to set up a direct connection, however you would probably be better off sending message via the server. This makes setting up group chats much easier. Each message could be prefixed with the ID of the intended recipient. For group chat it will will be prefixed with group ID. The server should keep a record of group ID's to find out who's in each group.

Help with MIDlets - TCP client server program

Hi I am new to using MIDlets, and I wanted to create a simple TCP client server program.. I found a tutorial in J2me forums and I am able to send a single message from server(PC) to client(Phonemulator) and from client to server. But I want to send a stream of messages to the server. Here is my program and I am stuck in the last step wher i want to send lot of messages to server. Here is my program, Could any one of u tell me how to do it? Or where am i going wrong in thsi pgm?
Code:
import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.microedition.io.Connector;
import javax.microedition.io.SocketConnection;
import javax.microedition.io.StreamConnection;
import javax.microedition.lcdui.Alert;
import javax.microedition.lcdui.AlertType;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.StringItem;
import javax.microedition.lcdui.TextField;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeExcepti on;
public class SocketMIDlet extends MIDlet
implements CommandListener, Runnable {
private Display display;
private Form addressForm;
private Form connectForm;
private Form displayForm;
private TextField serverName;
private TextField serverPort;
private StringItem messageLabel;
private StringItem errorLabel;
private Command okCommand;
private Command exitCommand;
private Command backCommand;
protected void startApp() throws MIDletStateChangeException {
if (display == null) {
initialize();
display.setCurrent(addressForm);
protected void pauseApp() {
protected void destroyApp(boolean unconditional)
throws MIDletStateChangeException {
public void commandAction(Command cmd, Displayable d) {
if (cmd == okCommand) {
Thread t = new Thread(this);
t.start();
display.setCurrent(connectForm);
} else if (cmd == backCommand) {
display.setCurrent(addressForm);
} else if (cmd == exitCommand) {
try {
destroyApp(true);
} catch (MIDletStateChangeException ex) {
notifyDestroyed();
public void run() {
InputStream is = null;
OutputStream os = null;
StreamConnection socket = null;
try {
String server = serverName.getString();
String port = serverPort.getString();
String name = "socket://" + server + ":" + port;
socket = (StreamConnection)Connector.open(name, Connector.READ_WRITE);
} catch (Exception ex) {
Alert alert = new Alert("Invalid Address",
"The supplied address is invalid\n" +
"Please correct it and try again.", null,
AlertType.ERROR);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert, addressForm);
return;
try {
// Send a message to the server
String request = "Hello\n\n";
//StringBuffer b = new StringBuffer();
os = socket.openOutputStream();
//for (int i=0;i<10;i++)
os.write(request.getBytes());
os.close();
// Read the server's reply, up to a maximum
// of 128 bytes.
is = socket.openInputStream();
final int MAX_LENGTH = 128;
byte[] buf = new byte[MAX_LENGTH];
int total = 0;
while (total<=5)
int count = is.read(buf, total, MAX_LENGTH - total);
if (count < 0)
break;
total += count;
is.close();
String reply = new String(buf, 0, total);
messageLabel.setText(reply);
socket.close();
display.setCurrent(displayForm);
} catch (IOException ex) {
Alert alert = new Alert("I/O Error",
"An error occurred while communicating with the server.",
null, AlertType.ERROR);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert, addressForm);
return;
} finally {
// Close open streams and the socket
try {
if (is != null) {
is.close();
is = null;
} catch (IOException ex1) {
try {
if (os != null) {
os.close();
os = null;
} catch (IOException ex1) {
try {
if (socket != null) {
socket.close();
socket = null;
} catch (IOException ex1) {
private void initialize() {
display = Display.getDisplay(this);
// Commands
exitCommand = new Command("Exit", Command.EXIT, 0);
okCommand = new Command("OK", Command.OK, 0);
backCommand = new Command("Back", Command.BACK, 0);
// The address form
addressForm = new Form("Socket Client");
serverName = new TextField("Server name:", "", 256, TextField.ANY);
serverPort = new TextField("Server port:", "", 8, TextField.NUMERIC);
addressForm.append(serverName);
addressForm.append(serverPort);
addressForm.addCommand(okCommand);
addressForm.addCommand(exitCommand);
addressForm.setCommandListener(this);
// The connect form
connectForm = new Form("Connecting");
messageLabel = new StringItem(null, "Connecting...\nPlease wait.");
connectForm.append(messageLabel);
connectForm.addCommand(backCommand);
connectForm.setCommandListener(this);
// The display form
displayForm = new Form("Server Reply");
messageLabel = new StringItem(null, null);
displayForm.append(messageLabel);
displayForm.addCommand(backCommand);
displayForm.setCommandListener(this);

Hello all,
I was wondering if someone found a solution to this..I would really appreciate it if u could post one...Thanks a lot..Cheerz

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

Re: is it possible to program with Sockets with the Internet as a network.

I am working with socket programming.
During the Christams holidays I will need to do some programming at home.
Is it possible to program with sockets on a home PC using Windows with only the Internet as a network?

yes it is
I am also working on an application that uses sockets at the moment, and I asked help a lot by these days ;)
Maybe I can help you from what I've learned..
here is a basic:
create server socket:
ServerSocket server = new ServerSocket(4444);
4444 is the port on which the socket is listening
Socket socket = new Socket("127.0.0.1",4444);
127.0.0.1 is a local IP adress to connect to and 4444 is the port number to connect to. That considers that the server and the connecting client are both on the same PC, but then you can use other IPs ;)
Hope it helps

Client/Server API with push?

I set up a simple Socket client server architecture with the Java socket API. However, my clients sometimes are initiators or requests, and sometimes my server is the initiator of infos. Example: client want to get infos from server but also want to tell the server something. The server tells all registered clients something but also can accept requests from clients. So both sides are client AND server (depending on what they currently want to do).
The socket API is just a classic client/server API, i.e. a server listens and a client sends requets and get responses. For my server to send requests to all clients, this is not enough. Is the only way to have all clients offering a socket server on their computer, too? so that this 2-way-request-communication works?
This is basically some kind of "push" technology, but i don't want my clients to "poll" the server just to emulate the feature of sending requests from the server to the client. Is there some other (perhaps non-socket) API that offers this?

@sjasja: how is the socket api symmetrical?It is, trust me! Connection initiation isn't, but after that it is. (Let's assume connected TCP/IP.)
The server does bind() and accept(), the client does connect(). After that, the connection is symmetrical: either end can issue any number of read() and write() calls in any order. You write() to a socket, it pops out from read() at the other end (though not necessarily as a single packet; TCP/IP is stream oriented, so write() "packets" can and will be glued together, or fragmented at the whimsy of network routers and friends.)
- accept() //wait for client to send request
- socket.getInputStream() //read request
- socket .getOutputStream() //write responseThose don't read or write; they get streams which you can read from and write to.
In the server, when accept() returns a new connection, you'd start a reader thread for that client. The thread would read() (or readLine() if you implement a line-oriented protocol) and handle the incoming messages. Whenever you want to write to the client, write to the stream returned by socket.getOutputStream(). You may need to synchronize writes if you have several threads that do sequences of write()s that need to arrive at the client sequentially.
As to the difficulty of socket programming: I don't think it particularly difficult. But then I've written dozens of socket programs since my first one in '85... The Java Tutorial socket chapter shows a simple client/server pair; not terribly difficult I think. In particular, check out the KKMultiServer at the bottom of the sample server chapter.

Client Server program using Applets for client

Creating a client server program using Applets for the clients.
Having problems distrubting the message from client to client
using ObjectOutputStreams/ObjectInputSteams.
I can connect each client to simple server and respond with by writting
the i/o stream of each client but unable to communicate from client to client. If any one out there has in tips of creating a class of objectOutputStreams that holds a array of ObjectOutputStreams and then broadcasts the message to every client, it would be much appreciated
Thanks.

Cheers poop for your reply
I never explained the problem properly. What it is I am trying to set up a Client Server program using Applets as the clients GUI. The problem is broadcasting the message to multiply client connnection(s).
Below is code, each client can connect and send message to the server. The problems is broadcasting the message to every client connection. The every client can input a message but only the last connected client can receive the message?????? Thanks in advance..
/*this my server class */
import java.io.*;
import java.net.*;
public class Server extends JFrame
private static final int ServerPort=8080;
private static final int MaxClients=10;
private ObjectOutputStream output=null;
private ObjectInputStream input=null;
private BroadCastMessage broadcastMessage;
public void runServer()
BroadCastMessage broadcastMessage= new BroadCastMessage();
try
{ //connect to server
ServerSocket s = new ServerSocket(ServerPort,MaxClients);
     //listen to port 5000 for new connections
     ///max is 25
     System.out.println("Server listening on port "+ServerPort);
while (state.isProgramRunning())
     try
     /// sGUI.waitForConnection();//new line
     s.setSoTimeout(100);
     //enable times in server-socket
     while (true)
     Socket incoming = s.accept();
     //wait and accept connnections from serverSocket
     //instance of the class,pases the new connection and message
     //spawn as a thread
     SocketConnection connection=new SocketConnection(incoming,broadcastMessage);
     Thread a = new Thread(connection); a.start();
     System.out.println(state.getConnectionCount()+"Connection received from :"+incoming.getInetAddress());
     catch(InterruptedIOException x){}
while (state.getConnectionCount()>0);
System.exit(0);
}catch (IOException e){}
public static void main(String[] args)
Server s =new Server();
     s.runServer();
/*this is my socket connection thread*/
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.net.*;
public class SocketConnection implements Runnable
private ObjectOutputStream out;
private ObjectOutputStream output=null;
private ObjectInputStream input=null;
private BroadCastMessage passOnMessage;
private Socket theConnection=null;
private String Inmessage="";
private int Ocount;
public SocketConnection(Socket caller,BroadCastMessage broadcastMessage,Ocount)
theConnection =caller;///(5000,n)
Ocount=ncount;
passOnMessage=broadcastMessage;
public void run()
try
getStreams();
processConnection();
catch(Exception e)
{String clientDetails=("connection from IP Address: "+theConnection.getInetAddress());}
private synchronized void getStreams() throws IOException
{ //get streams to send and receive data
//set up output buffer to send header information
///Ocount++;
//create new objectoutputstream
output=passOnMessage.getOutputObject(output,theConnection,Ocount);
///flush output buffer to send header info.
Ocount++;
//set up input stream for objects
input =new ObjectInputStream(
theConnection.getInputStream());
System.out.print("\nGot I/O streams\n");
private synchronized void processConnection()throws IOException
//process connection with client
String Outmessage =" count : "+status.getConnectionCount();
//send connection successful message to client
     Outmessage=Outmessage+"SERVER>>>Connection successful";
     output.writeObject(Outmessage);
output.flush();
do ///process messages sent from client
     try
     Inmessage = (String) input.readObject();
     System.out.println(Inmessage);
     /* //while the connection is open each line
     that is passed from the client to the server
     is read in and is displayed*/
     messageDetails.setMessage(Inmessage);
     String CurrentMessage=messageDetails.getMessage();
     //output.writeObject(CurrentMessage);
     // output.flush();
     passOnMessage.FloodMessage(CurrentMessage);
     //sending out the message
catch(ClassNotFoundException classNotFoundException){}
}while (!Outmessage.equals("CLIENT>>>TERMINATE"));
/*this my attempt at broadcasting the message to all clients
my thinking was that you could create a array of objectoutputstreams
which in turn could be broadcasted(bit confussed here)*/
import java.io.*;
import java.net.*;
public class BroadCastMessage /// implements Runnable
private int count;
private String Inmessage="";
private ObjectOutputStream temp=null;
private ObjectOutputStream[] output = new ObjectOutputStream [12];
//temp level of array of objects
public BroadCastMessage()
count=0;
public synchronized void FloodMessage(String message) throws IOException
System.out.print(count);
     for(int i=0;i<count+1;i++)
     try
{ System.out.print(count);
     output[count].writeObject(message);
     output[count].flush();
     catch(IOException ioException)
{ioException.printStackTrace();}
     notifyAll();
public ObjectOutputStream getOutputObject(ObjectOutputStream out,Socket caller,int Ocount)
try
{ temp = new ObjectOutputStream(caller.getOutputStream());
     AddObjectOutputStream(temp,Ocount);
////FloodMessage();
     catch(IOException ioException)
{ioException.printStackTrace();}
return temp;
public void AddObjectOutputStream(ObjectOutputStream out,int Ocount)
{ ///add new object to array
count=Ocount;
output[count]=out;
System.out.print("\nthe number of output streams : "+count+"\n");
}

HELP:USING CLIENT SERVER PROGRAM ON DIFF.MACHINES CONNECTED TO INTERNET?

BELOW IS THE JAVA CODE FOR CLIENT & SERVER PROGRAM (TCP) USING SOCKET.
I AM TRYING TO RUN CLIENT & SERVER PROGRAM ON 2 DIFFERENT MACHINES CONNECTED 2 INTERNET
(1 RUNS SERVER.java & OTHER CLIENT.java).
IS IT POSSIBLE WITH THE CODE WRITTEN BELOW?
// Server.Java
import java.net.*;
import java.io.*;
class Server {
public static void main(String[] args) {
boolean finished = false;
try{
ServerSocket listener = new ServerSocket(4444);
while(!finished)
{Socket to_client = listener.accept();
OutputStream out = to_client.getOutputStream();
PrintWriter pout = new PrintWriter(out, true);
pout.println("Hello! this is server talking to you.");
to_client.close();
listener.close();
}// end of try
catch(Exception ie) {
System.out.println(ie);
//Client.Java
import java.net.*;
import java.io.*;
class Client
public static void main(String[] args)
Socket client;
String host="serverpcname";//host is assigned name of the server
try
{InetAddress adressen = InetAddress.getByName(host);
client = new Socket(adressen,4444);
BufferedReader scanf = new BufferedReader(new
InputStreamReader(client.getInputStream()));
String someString = scanf.readLine();
System.out.println("From Server: "+someString);
client.close();
catch(Exception e)
System.out.println(e);
WHEN THE CODE IS EXECUTED(CLIENT.java ON 1 PC & SERVER.java on other) IT GIVES FOLLOWING EXCEPTIONS:
java.net.UnknownHostException: serverpcname: serverpcname
PLZ. GUIDE ME.
THANKS IN ADVANCE.

For a server to be accessible on the inetrnet it needs to have an externally visible IP address. For example, an address which starts with 192.168.1 is for internal use only can only be used by other machines on the same internal network. The server's firewall needs to allow the port you are using access and the client has to be able to lookup up the IP address either using the hosts file or via a DNS service. None of these things have anything to do with Java programming, so if you have any more questions I sugegst you try googling them or ask a forum which relates to these issues.
The connection time out is due to the fact that there is no way to contact an inetrnal address over the inetrnet. The host unknwown means you haven't configured your PC to lookup that address. i.e. the host is unknown.

About the communication issues in the client-server program

About the communication issues in the client-server program
Hi, I have some questions about the communication issues in a java project, which is basically the client and server architecture. In brief, the client, written in java, can be deployed anywhere, and in the following part, assume it is in the LAN (Local Area Network) which is connnected to the internet through the firewall and/or proxy, and the server, written in
java too, simply provides the listening service on a port in a remote machine. And assume the server is connected to the internet directly so that the scenario can be simple to focus on the core questions.
My questions are as follows:
1 About the relationship between the communication port and protocol
Generally, protocols at the application level like HTTP, FTP have their own default port, e.g., HTTP is corresponding to 80,
FTP is to 25. But it is NOT necessary for the web server to provide the HTTP listening service at port 80, right? E.g, Tomcat provides the HTTP listening service at 8080. So it means the default relationship between the application protocl and their port is some routine, which is not necessary to follow, right?
2 Assume a LAN connected to the internet through a proxy, which only allows HTTP protocol, then questions are:
2.1 Does the proxy recognize the HTTP request from the client by the port number (carried in the request string)? For example, when the server provides the HTTP listening service at 80, then the request from the client will include the port number 80, then the proxy will parse such info and decide if or not the request can be out.
2.2 Does the proxy recognize the HTTP request from the client by protocol (carried in the request string)? For example, the protocol used in the communicatin should be included in the request, then the proxy can parse it to make the decision.
3 In java programm, if using the HTTP protcol, then on the client: the corresponding API is java.net.URLConnection, right?
If using the TCP protocol directly, then on the client:the corresponding API is java.net.Socket, right? In both cases, the server side use the same API, java.net.ServerSocket?
Is it correct to say that the communication by Socket is faster than URLConnection?
4 Take MSN messenger for example, which protocol does it use? Since proxy configure is only the possible option, so I guess generally the TCP protocol is used directly so that the better perfomrance can be achieved, right?
5 Given 3 computers within the same LAN, can the client, proxy, server environment above be correctly simulated? If so, can
you recommend me some typical proxy program so that I can install it to configure such an enviroment to perform some test?
6 I guess there should be some software to find out which port number a given program/process is going through to connect to
the remote machine, and which port number a given program/process is listening on? Also, what protocl is used in the given
communication.
7 Finally, regarding each of the above questions, it will be highly appreciated that if you can recommed some references,
tutorials, books etc. In summary, what I care about is how to enable the java client behind the proxy and firewall to
communicate with the remote server without problems, so if you know some good tutorials plz let me know and thx in advance!
Finally, thanks for your attention so such long questions =).

FTP is to 25. But it is NOT necessary for the web
server to provide the HTTP listening service at port
80, right? E.g, Tomcat provides the HTTP listening
service at 8080. So it means the default relationship
between the application protocl and their port is
some routine, which is not necessary to follow,
right?Not sure what you're saying here.
There must be a server listening on some port. The client must know what port that is. If you open the connection using the Socket class, you'll explicitly specify the port. If you use some higher level class like URLConnection or something in the commons Net package, there's probably a default port that will be used if you don't explicitly specify another.
There's no way for the client to know that the HTTP request will go to port 80 instead of port 8080. If you think the the client contacts the server without explicitly naming a port, and then asks the server "get me your HTTP server", and the port is determined from that, you're mistaken.
Not sure if you're thinking that, but it sounded like you might be.
2 Assume a LAN connected to the internet through
a proxy, which only allows HTTP protocol, then
questions are:
2.1 Does the proxy recognize the HTTP request
from the client by the port number (carried in the
request string)? For example, when the server
provides the HTTP listening service at 80, then the
request from the client will include the port number
80, then the proxy will parse such info and decide if
or not the request can be out. I'm not sure, but I think most proxies and firewalls are configured by ports. I thought I'd heard of more sophisticated, higher-level ones that could understand the content to some degree, but I don't know anything about those.
3 In java programm, if using the HTTP protcol,
then on the client: the corresponding API is
java.net.URLConnection, right?That's one way.
You might want to look into this:
http://jakarta.apache.org/commons/httpclient/
If using the TCP protocol directly, then on the
client:the corresponding API is java.net.Socket,
right? In both cases, the server side use the same
API, java.net.ServerSocket? A Java client will user Socket, and a Java server will use ServerSocket and Socket.
Is it correct to say that the communication by Socket
is faster than URLConnection?Probably not.

Client server programming

Hi;
I want to learn client server programming on using windows xp for the client and windows server 2003.
I downloaded the 9.2 windows xp database version for the client . What do I need to download for the server? I see that there is a 32 and 64 bit version for the server.
Thanks for your help!

What I was asking is what should I install on the server
the 32 or 64 bit version of oracle?
I want to learn how to write client/server programs using Oracle.
I have a network at home with one computer serving as the client and another has server 2003 on it.
Again Thanks for your help!

Design Pattern for multithreaded client server program

I asked this question in another post, but with other stuff, so I'll distill this one.
I am creating a multi-threaded client server program (just for learning - a chat program at this point). I built the server and client in swing, and I'm wondering what the best design pattern is for this setup. Right now all the swing stuff is in the MyServer class. In that class I have a loop accepting client connections to the serverSocket and creating a new MyServerThread (threaded client connection).
The problem is that all the work of creating input streams, interacting with the server, all that stuff is done in the MyServerThread class, but I want that text to be written up to the Swing objects - which is in the MyServer class. So right now in the MyServerThread class I pass the MyServer object into it, but I'm not sure if that is really the most robust thing to do. Does anybody have any suggestions as to how this should be done. If somebody has an article they'd like to point to I'll check it out too. But if it's just the run-of-the-mill multithreaded client-server article, I've read alot and most don't specifically address my question.

Thanks for the reply Kaj, and I think I'll keep my design for now, since it's just quick and dirty. I've read the MVC concept a while ago and I'll revisit it again when I get more serious. But I have a question, why should I be using a callback interface, why an interface at all? And then make MyServer implement that interface...why not just pass MyServer to the thread object? Or is there something down the line that I did not forsee?

About send TCP package to other server program with the ABAP

I have a server program, it receipt the tcp data package,then process,then return the result with tcp package.
the data come from the sap system.
for example, the material master record.
I can use the abap to get the data,but i have no idea to send the data to server progam and receipt the result.
How to do it? Who can help me.Thanks a lot.
Best regards.
LnSinco.

> As an experiment, I tried going the other way. That it, I started up the
> Simple Data Server VI on the Windows PC. I then "pointed" my SGI client at
> the server on the PC. It works, ... sort of. I am getting an
> appropriately sized list of numbers displayed on the SGI host, but while
> most look like floating point values, some look like VERY large integers.
>
> I believe I have a data representation problem. That is, I don't know if I
> should expect to send (server-side) or see (client-side) C programming
> variables of type 4-byte floats, 8 byte doubles, or something else. Also, I
> am not certain how many values I should expect to send/see in each message.
> I think the default for the Simple Data Client/Server programs is 200
> points
, but I am not sure what that really means, either.
>
By default, LV converts all of the datatypes to be in big endian form.
I'm not sure about your SGI, but if it is a little endian machine, then
that will cause problems. If that is the case, you will want to swap
the words and bytes of the four byte values.
To debug this more easily, you might just make sure you send over very
predictable data such as 0, 1, 2, 3, etc. Lots of times these are
tested with random data, but that makes it pretty hard to see a pattern
when the data is wrong.
Greg McKaskle

Client Server Application with images or icons

I made a Client Server application with JFrames, but I put a jLabel with an icon, and I can't run the Client.
It says java.lang.NullPointerException
Do you know why I can't see the icon in the JLabel? It isn't an applet, it's an application with JFrames.

You have to explain the problem better if you want some help. Also show the code which is giving you the nullpointerexception(Do not forget codetags!).

Client/server application using sockets

Hi there,
I'm trying to create a client/server application using sockets where the client has a GUI of a membership application form for some sort of club. Basically, the user will enter their name, address, membership no. etc in to various Jtext fields and then press a JButton to submit these details to the server. The server will then hopefully just dump these details to a text file.
Can anyone give me any examples, ideas on how to start, links etc.
Thanks v. much in anticipation,
Nick

Take a browse of the tutorial on sockets: http://java.sun.com/docs/books/tutorial/networking/sockets/clientServer.html

White Paper: End-to-End Client/Server Security with the Adobe Flash Platform

Today we released a sorely needed white paper on end-to-end client/server security with the Adobe Flash Platform. This information is directly applicable to the Adobe LiveCycle family as well as Flash RIAs.
http://www.slinnbooks.com/books/enterprise/securityWhitePaper.shtml
Thank you,
Mike
Michael Slinn
http://micronauticsresearch.com
http://slinnbooks.com

Hai,
Delete the certificate in the ABAP system and try importing the new certificate from the EP instance(ADS) and export into the ABAP and check...
Thanks and Regards,

Client-Server programming with Sockets

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