HTTP Client/Server program problems
Hi all,
I am doing an exercise in which I create a Client and Server program. I send a GET request but nothing seems to happen. There is obviously something I'm missing. Could it be a badly formed request? The code is below. Any help is appreciated.
Client program.....
import java.io.*;
import java.net.*;
import java.util.StringTokenizer;
public class HTTPClient{
String host, path;
int port;
public static void main (String argv[]){
new HTTPClient(argv[0]);
public HTTPClient(String url){
try{
URL myURL = new URL(url);
host = myURL.getHost();
port = myURL.getPort();
System.out.println("Port = " + port);
if (port == -1) port = 30280;;
path = myURL.getPath();
if (path.equals("")) path = "/";
Socket s = new Socket(InetAddress.getByName(host), port);
sendRequest(s.getOutputStream());
printResponse(s.getInputStream());
s.close();
catch(MalformedURLException murl){
System.out.println("Badly formatted URL " + murl.getMessage());
catch(IOException e){
System.out.println("Problem initialising socket " + e.getMessage());
public void sendRequest(OutputStream out){
StringBuffer buf = new StringBuffer();
buf.append("GET /AC095.html HTTP/1.1\r\n");
buf.append("Host: http://students.odl.qmul.ac.uk\r\n\r\n");
try{
out.write(buf.toString().getBytes("US-ASCII"));
catch (IOException e) {System.out.println(e.getMessage());
public void printResponse(InputStream in){
try{
while (in.available() <= 0)
Thread.sleep(500);
while (in.available() > 0)
System.out.print((char) in.read());
System.out.println ("");
catch (IOException e) {
System.out.println(e.getMessage());
catch (InterruptedException ie) {
System.out.println("Error waiting for response " + ie.getMessage());
/* Read in the response from the HTTP server and print it out */
}Server code......
import java.io.*;
import java.net.*;
import java.util.*;
public class HTTPServer{
String version = null;
public String httpVer;
public static void main(String argv[]){
new HTTPServer(Integer.parseInt(argv[0]));
public HTTPServer(int port){
boolean listening = true;
try{
ServerSocket ss = new ServerSocket(port);
System.out.println("HTTP Server running and listening for requests...");
while (listening){
Socket mySocket = ss.accept();
InputStream in = mySocket.getInputStream();
readHeaders(in);
String response = getResponse();
OutputStream out = mySocket.getOutputStream();
out.write(response.getBytes("US-ASCII"));
out.flush();
mySocket.close();
catch(Exception e){System.out.println(e.getMessage());}
private String getResponse(){
StringBuffer responseBuf = new StringBuffer();
responseBuf.append (httpVer + " 200 OK\r\n");
responseBuf.append ("Content-type: text/html\r\n");
responseBuf.append ("Content-length: 119\r\n");
responseBuf.append ("<HTML>\r\n");
responseBuf.append ("<TITLE> My served web document </TITLE>\r\n");
responseBuf.append ("</HEAD>\r\n");
responseBuf.append ("<BODY>\r\n");
responseBuf.append ("<H1> Hello from the server! </H1>\r\n");
responseBuf.append ("</BODY>\r\n");
responseBuf.append ("</HTML>\r\n\r\n");
String responseStr = responseBuf.toString();
responseStr = responseStr.trim();
return "";
private void readHeaders(InputStream in) throws IOException {
StringBuffer sbuf = new StringBuffer();
int ch;
String clientStr;
//This loop reads in all of the input until there is nothing left to read.
//All of the characters are appended to the string buffer.
while ((ch = in.read()) != -1) {
sbuf.append((char) ch);
//clientStr will hold string in string buffer without any leading or
//trailing white space.
clientStr = sbuf.toString();
clientStr = clientStr.trim();
//Split clientStr into substrings and store them in an array.
String [] tokens = clientStr.split(" ");
//Obtains HTTP version
httpVer = tokens [2];
}Cheers,
Chris
I've written out.flush() in the server program. When I attempt to connect to the server it just hangs. I've modified the code locally to request a webpage from elsewhere and it works so it can't be the format of my GET request. I assume that the problem has to be in the Server program. Is it not reading in and understanding the /r/n properly?
Similar Messages
-
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. -
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 -
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");
} -
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?
-
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! -
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 -
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. -
Client/server program validation - is it possible?
I've been mulling over this problem for a few days, and am starting to wonder if it's theoretically possible to find a solution. I'm not looking for specific code, this probably won't even be implemented in Java, I'm just wondering if there is a theoretical program model that would work in this situation.
The short version:
Validate the data generated by a client program, without knowing the original data.
The long version:
This is a "profiling" system for a MMOG (Massively Multiplayer Online Game). The MMOG is an internet based client/server graphical program where each client connects to the server and they interact with each other and the virtual world. They pay a monthly fee for access to the game. My program is not affiliated with the MMOG or its makers. I have no connections inside the company and cannot expect any cooperation from them.
The "profiling" system is also a client/server model. The client program runs in the background while the MMOG client is active. It accesses the memory of the MMOG client to retrieve information about the player's character. Then, possibly on request or maybe immediately, it sends the character data to our server.
What I want to validate is that the character data being sent is unmodified and actually comes from the MMOG program.
I can reasonably expect that with mild encryption and some sort of checksum or digest, the vast majority of problems can be avoided. However, I am not sure it's possible to completely secure the system.
I assume that the user has access to and knowledge of the profiler client and the MMOG client, their assembly code, and the ability to modify them or create new programs, leveraging that knowledge. I also assume that the user does not have access to or knowledge of either of the server applications - the MMOG server or mine.
In a worst-case scenario, there are several ways they could circumvent any security I have yet been able to think of. For instance, they could set up a fake MMOG client that had the data they wanted in memory, and let the profiler access that instead of the real thing. Or, they could rewrite the profiler to use the data they wanted and still encrypt it using whatever format I had specified.
I have been considering using some kind of buffer overflow vulnerability or remote execution technique that would allow me to run specific parts of the client program on command, or get information by request, something that could not be anticipated prior to execution and thus could not be faked. But this seems not only insecure for the client but also not quite solid enough, depending on how it was implemented.
Perhaps a series of apparently random validation codes, where the client does not know which one actually is doing the validation, so it must honor them all. Again, this is very conceptual and I'm sure that I'm not explaining them very well. I'm open to ideas.
If I don't come up with anything better, I would consider relying on human error and the fact that the user will not know, at first, the relevance of some of the data being passed between client and server. In this case, I would include some kind of "security handshake" that looks like garbage to the client but actually is validated on the server end. A modified program or data file would result in an invalid handshake, alerting the server (and me) that this client was a potential problem. The client would have no idea anything had gone wrong, because they would not know what data the server was expecting to receive.
I hope I have not confused anyone too much. I know I've confused myself....Yes, that is the general model for all MMOGs these days - no data that can actually affect the game is safe if loaded from the client's computer. All character and world data is sent from server to client and stored in memory. Any information that is saved to the client's computer is for reference only and not used by the game engine to determine the results of actions/events etc.
My program accesses the MMOG client's memory while the game is running, and takes the character information from there. It does not have direct access to the MMOG server, and does not attempt to modify the data or the memory. Instead, it just encrypts it and sends it to our server, where the information is loaded into a database.
The security issue comes into play because our database is used for ranking purposes, and if someone were to hack my program, they could send invalid data to our servers and affect the rankings unfairly.
I'm just trying to think of a way to prevent that from happening. -
Multiple Clients in Client/Server Program
I'm currently trying to make a small Client/Server application that will mimic a very basic chat room program. The basic idea is that the Server side of the program is started and multiple Client programs can connect and communicate with each other. However, I'm having a few problems at the moment, mostly with figuring out how it can work.
Firstly, I can communicate one to one with the server and the client as the client socket is stored in a variable. However, to make it possible to allow multiple connections I've used a thread for each new connection but I'm not sure how I can broadcast messages to every connection. Would it be safe enough to store each client socket in a list and then communicate that way? Not sure what will happen when the client disconnects though it seems to be an issue.
I'm also not sure how every message can be broadcasted to every single connections to the server. The server program can send a message to every client but the clients message at the moment only goes to the server. Anyway here's a bit of my code so far:
SwingWorker<Socket, Void> worker = new SwingWorker<Socket, Void>() {
protected Socket doInBackground() throws Exception {
// Client socket
try {
while (!stopRequested) {
clientSocket = serverSocket.accept();
// Stop requested is checked twice because the accept() method
// waits for a connection
if (!stopRequested) {
HostFrame.getFeedbackTextArea().append("New Connection Found");
Thread clientThread = new HandlerThread(clientSocket);
clientThread.start();
else {
serverSocket.close();
clientSocket.close();
catch (Exception e) {
HostFrame.getFeedbackTextArea().append("Failed to Connect with Client");
System.out.println(e.getMessage());
return clientSocket;
};The SwingWorker is used so that the GUI doesn't freeze when the server tries to find a connection. At the moment it just creates a thread for each new connection but I'm guessing this isn't what I'm going to be needing to handle more than one client. Also at the moment I have no way of directing a message to a specific socket I'm pretty much just using the standard method shown on the Sun website about Sockets. Any help would be much appreciatedclientSocket = serverSocket.accept();'clientSocket' should be a local variable here.
else {
serverSocket.close();
clientSocket.close();You shouldn't close 'clientSocket here'. All you're accomplishing is closing the most recently accepted client socket. What about the others? Generally speaking you should let the client-handling threads take care of their own sockets completely.
return clientSocket;This return statement is meaningless. You may as well return null. SwingWorker doesn't care. Don't just return something because you've got it lying around. In this case you shouldn't have it lying around.
At the moment it just creates a thread for each new connection but I'm guessing this isn't what I'm going to be needing to handle more than one client.That is exactly what you have to do to handle more than one client. Once you fix it as per above.
Also at the moment I have no way of directing a message to a specific socket I'm pretty much just using the standard method shown on the Sun website about Sockets.You probably need to keep a Map of client sockets accepted, keyed by some client identifier. -
Need help with HTTPS Client/Server
Hi i really dont know much about this topic and i was wondering if any 1 knows where to find a good example program to set up a
HTTPS Server/Client or at least how to implemnt a HTTPS Client.
thanks in advanceURL.openConnection works fine as a client. You don't have to do anything other than specify the protocol as https.
I don't know what you are looking for in terms of server. Are you trying to write your own server? Which part do you not know? The HTTP part or the S part? -
Client/server program: Urgent, pls help!!
I am new to Java, particularly Networking in Java, while writing client/server application I have got completely strucked now. Can any one give me an idea where I am wrong?
I am writing a simple client server application in Java using Socket and ServerSocket classes as a part of my course work. Through client I am just establishing connection with server, getting user inputs/commands, sending the same input to server (server will capitalize this input and return it back to client), receiving and displaying server�s response.
The connection is established fine. Even it is accepting users input well but I am getting runtime NullPointerException while trying to send it to server. Here is the working of my client command window.
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>javac TClient.java
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>java TClient
Enter the message
hello
Exception in thread "main" java.lang.NullPointerException
at TClient.Send_Message(TClient.java:46)
at TClient.main(TClient.java:76)
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>
As soon as I get this exception the connection with server is lost and I get this in server command window.
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>javac TCPServer.java
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>java TCPServer
Exception in thread "main" java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:168)
at java.io.ObjectInputStream$PeekInputStream.read(ObjectInputStream.java
:2150)
at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream
.java:2163)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputS
tream.java:2631)
at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:734
at java.io.ObjectInputStream.<init>(ObjectInputStream.java:253)
at TCPServer.main(TCPServer.java:17)
C:\Program Files\j2sdk_nb\j2sdk1.4.2\bin\abc>
Here is my code for server (TCPServer.java)
import java.io.*;
import java.net.*;
class TCPServer {
public static void main(String argv[]) throws Exception
String clientSentence;
String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(80);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
ObjectInputStream inFromClient = new ObjectInputStream(connectionSocket.getInputStream());
ObjectOutputStream outToClient =
new ObjectOutputStream(connectionSocket.getOutputStream());
clientSentence = (String ) inFromClient.readObject();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeObject(capitalizedSentence);
And this is for Client (TClient.java)
import java.io.*;
import java.net.*;
import java.util.*;
class TClient {
private ObjectOutputStream server_output;
private ObjectInputStream server_input;
private Socket client;
private void server_connect() throws IOException
client = new Socket(InetAddress.getLocalHost(), 80);
private void getstreams() throws IOException
server_output = new ObjectOutputStream (client.getOutputStream());
server_output.flush();
server_input = new ObjectInputStream(client.getInputStream());
private String get_cmd_frm_usr() throws IOException
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
String sentence;
System.out.println("Enter the message");
sentence = inFromUser.readLine();
/*StringTokenizer st = new StringTokenizer(sentence);
while (st.hasMoreTokens()) //separating n printing words of inputted sentence
System.out.println(st.nextToken());
return(sentence);
private void Send_Message(String msg) throws IOException
//System.out.println("within send_message method :"+ msg);
server_output.writeObject( msg );
server_output.flush();
private void recieve_n_disp_mess() throws Exception
String modifiedSentence;
modifiedSentence = ( String ) server_input.readObject();
System.out.println("\n\n by SERVER: " + modifiedSentence);
private void close_connection() throws IOException
client.close();
public static void main(String args[]) throws Exception
TClient client = new TClient();
try{
client.server_connect();
String command=client.get_cmd_frm_usr();
//System.out.println("this is returned from input method n ready to sent to server soon: "+ command);
client.Send_Message(command);
client.recieve_n_disp_mess();
client.close_connection();
} catch(EOFException eofException) {}
catch (IOException ioException) {}you never initialized the server_output and the server_input vriables...
I see you have the getstreams() function which should initialize them but you never call it...
so untill you will call it those variables will stay null.
I can also see you do not implement constructors, its much easier just to implement these instead of functions initializing variables...
Hope it will help
private void getstreams() throws IOException
server_output = new ObjectOutputStream
(client.getOutputStream());
server_output.flush();
server_input = new
ObjectInputStream(client.getInputStream());
public static void main(String args[]) throws
Exception
TClient client = new TClient();
try{
client.server_connect();
String command=client.get_cmd_frm_usr();
//System.out.println("this is returned from input method n ready to sent to server soon: "+ command);
client.Send_Message(command);
client.recieve_n_disp_mess();
client.close_connection();
} catch(EOFException eofException) {}
catch (IOException ioException) {} -
To:NOAH:REGARDING CLIENT/SERVER Program
Dear Noah,,,how to run the server program since there is no component inside?Pls reply
Noah.
can u pls send the client porgram so i can run the program and see.Got one point i still doesn;t understand
which is jdk only allow user to run JAVAC *.java one time
if i run the server ,how could i run the client? -
An rmi client server design problem
I am implementng a networked cards game in java using rmi . The server keeps track of the turn of the players and activates ther clients(on an applet) whose turn it is to play .
Both client and server call each others methods.
Prblem one :
Right now if a a client disconnects , a process run through all the clients active and gets a remote exception on the server and removes ALL the 4 players i nthat particulat group. If I want to save the state and allow any player to contuniue from there , how will I do it?
Problem 2:
How do I keep track of the time a client takes to play.
If he takes longer than say 5 mintes , I should disconnect him.There seem to be two issues at stake: <b>catching the remote exception</b> and <b>multithreading</b> your application on the server.
When a client disconnects "suddenly" (without logging off via remote method call to alert server), the remote method call by the server to all <i>n</i> players triggers a remote exception that must be caught and dealt with accordingly (do I understand that it is causing the application to exit at present?) When caught, you must identify which player is "gone" and remove that client from the pool of client objects.
Right now, it sounds as if the app is NOT multithreaded. You can create a low-priority thread that looks at a time variable for each player to determine its last moment of play. This means every successful remote call from client-server or vice-versa will update that client's 'lastplayed' variable with (long) System.currentTimeMillis() for example. -
Uml and client server programming
I m developing chat messenger. i am finding difficult to apply uml on this type of software (client server).can any one give me sample documentation or tutorials
UML can express and communicate your
ideas for sure, but it's not where to start with the
high level architecture unless you have an idea about
how to achieve it.
Once you have an idea of how it should work, then the
activity diagrams/sequence diagrams/collaboration
diagrams will just drop out of you and into the model.Actually, UML usually is the first place to start. Specifically, the Use Case diagram is often the starting point in designing a system. The first iteration of these diagrams will be very rough for sure, but what better way to begin discovering the functionality of a system than to (at a very high level) determine who's gonna use the system and how they are going to use the system.
A common practice is to get a sheet of paper and draw a line down the middle (making two column). Label them actors (left colum) and processes (right column). Starting with the right column, list (again, at a very hight level) the thins that your system should do. Repeat this for the left column, this time thinking of the "types" of users that will use the processes you've just listed. Then you draw lines from the actors to the processes and this is the begining of your use cases. The next steps is to start storyboarding the use cases. This forces you to think of what each process does in in a little more detail. From there, you will begin to see common behavior and even new use cases. It takes a few iterations to fully discover and realize use cases, but you start with the 10,000' view of it this way.
For example (and this is just an example):
actors processes
System Post a message
Authenticated User Read a message
Anonymous User Delete a message thread
Administrator Login
Logout
Register
Update Profile
Generate Audit EntryWhen you draw the lines from actors to processes in the above example, you'll note some the following:
1. System can Generate Audit Entry
2. Authenticated User can Post a message, Read a message, Logout and Update Profile
3. Anonymous User can Reade a message, Login and Register
4. Administrator can Post a message, Read a message, Delete a message thread, Logout and Update Profile
Again, this is just an example. You should see that it give you a bird's eye view of the services to be provided by your system and who can use those services. When you begin realizing your use cases (the processes in the above example), you will begin to see behavior that is common to many services. These behaviors are what will begin helping you to eventually make architecture level decisions.
Maybe you are looking for
-
6.0 ~ Webpage not functioning as before
The doppler radar site: http://www.weatheroffice.gc.ca/radar/index_e.html?id=WHK has an animation feature that we use constantly to track storms heading our way. The animation plays a sequence of frames taken over a period of time. In every version
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How do I access In Design tool from my Adobe CS5 Production Premium?
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i have a problem in writing a query. It is a simple select having a "IN" clause, the values of which are created dynamically. Now since the IN clause could exceed 1000 values at a time, im using it as shown below select * from table where (col1 in ()
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How to get source from ListSelectionListener on Table?????????
hi there i have about three JTables in my application, i have added ListSelectionListener to these tables to see if any selection was made on them. Table1.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); ListSelectionModel rowSM = Table1.getSel
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For the life of me I can't remember how to do this. I have a query: SELECT username FROM ecae WHERE username NOT IN (#listsent#) where #listsent# is a comma delimited list. I know in these cases I need to wrap each entry in the list in single quotes,