I have all of my code written, but it is not producing any output and i'm not sure why.
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
[code]...
This question has confused me because "Errors" are capitalized and I'm not sure what they mean.
To me this question is false. Sockets can be used to transfers file over a network.
I can't see why this wouldn't work. The code looks fine to me.
I don't think this is true unless you're using the mouseEntered() or mouseExited() method. But again, I'm not sure.
I think this is true, I don't know what else could have listeners.
They're only worth a few marks each so the answer is only suppose to be a line or two. They are all true or false questions that require an explanation.
I have just started learning about sockets and such... and i have created a chat program with a server and a client
server:
public class Server {
private static ServerSocket server;
private static Socket connection;
private static PrintWriter pw;
private static BufferedReader br;
private static JTextField textOutput;
[Code] ....
so, everything is working fine . There is only one thing i would like to do now: make it so that i can run the server from my computer and then others can run the client from theirs and we will be able to chat . So I tried:
In the client code on line 56 is says:
connection = new Socket("localhost",7777);
So I changed "localhost",7777 to "myip",7777)
But when i run the server on my computer and run the client on another computer i get this error:
java.net.ConnectException: Connection refused: connect
Why is the connection getting refused? is it for security reasons? so hackers cant connect to me or something? And is there a way to tell your computer to allow that client to connect?
I am having a problem passing an int value from one class to the other. The gist of the objective of this program is to compute a local sum at each client, and then once the local sums are computed.. to compute the overall sum from all the clients. My problem is that I'm having trouble figuring out how to pass each sum from each individual client in the class multicastSenderReceiver to the readThread class. I keep getting an error.
I feel that I have to be able to pass the sum value from each client generated in multicastSenderReceiver to the other class, because that is the only way I'll accurately be able to sum up all the values..
Java Code:
package multicastsenderreceiver;
import java.net.*;
import java.io.*;
import java.util.*;
//import static multicastsenderreceiver.multicastSenderReceiver.numProcesses;
class multicastSenderReceiver{
[code]....
I'm writing a small program in Java to simulate a shopping cart. A shopping cart has an array og objects Item. As a console application, my program runs.But, in the GUI version, I have some issues. In class MainMenu I create a ShoppingCart object, named "cart"(line 103)In class AddItemMenu I create an Item object, and I want to add it in my ShoppingCart object "cart".BUT, AddItemMenu cannot "see" variable "cart".
//MainMenu.java
package shoppingcartgui;
public class MainMenu extends javax.swing.JFrame {
public MainMenu() {
initComponents();
[code]....
Generally Socket Programming uses HTTP Protocol to send and receive messages in Java. Can we try to exchange HTTP/HTTPS requests instead of TCP?
a Socket constructs a HTTP request to send to another socket from information it has and sends to another one and Server responds with HTTPResponse.
I'm new to java and haven't develop any application before that... I need to develop an application through which i can send data from 1 computer to another computer. These communication in between the computers are those are under one router connection. Means they can connect even without internet access
Main concept is as follow
1. Java application on computer A [server side application]
2. Java application on Computer B [Client side application]
3. Java application on computer C [Client side application]
Now computer B and C communicate with computer A. but they don't know about presence of each other
I created an instant messenger using java. When I have the Server that communicates between the clients and one client running on my Computer the CPU Usage is at 100%. It really slows down everything else I'm doing and I figure this might be an issue if I gave this to people to use. I don't want the client taking up a lot of CPU Usage if they're just running it in the background while doing other things on their computer. The program utilizes multithreading. Each thread is constantly being polled for input.
The Server, as seen below, has two threads. I explain what the threads do before the code. There is also another while loop running constantly in the server that is waiting for sockets to connect. The loop does not run constantly at the line socket.accept(); it stops and just waits.
The User, split into a menu and chat window, has two threads as well. I explain what the threads do before the code. After I originally posted I put a 100 ms sleep in all my threads. CPU Usage is still at 100%*
This thread listens for input from the user. The input tells the server what action to take. There is a thread running for every user currently connected to the server.
public void run()
{
try
{
input = new DataInputStream(user.getSocket().getInputStream());
output = new DataOutputStream(user.getSocket().getOutputStream());
[code]....
I'm deployed application A and application B in TOMCAT server applications, the U1 user enters into the application A, he authenticates and generates a call to a page of the app B. As I was able to access the session of user U1 en A from B, it could have a single session.
View Replies View RelatedI have written a java code to transfer files from one server to another using the concept of socket programming. I got the codes from another java forum that meet my requirements. The program is said to transfer large sized files (like .mkv , .mprg movies) from one machine to another and can be used to transfer files of all formats. But after running the codes I found that the program is not able to transfer large sized files such as movies and even pdf of sizes 80mb or 111mb. When i transfer small sized files, it gets transferred and the output shows that. You can run the codes and observe it. But when i try to transfer large sized files, the program goes on running for hours. The large sized files are not getting transferred. The program has used bytebuffer but still this error occurs.
**ClientMain.java**
import java.io.IOException;
import java.net.Socket;
public class ClientMain
[code]....
Note that:-
1. ClientMain.java and DirectoryTxr.java are the two classes under client application.
2. ServerMain.java and DirectoryRcr.java are the two classes under Server application.
3. run the ClientMain.java and ServerMain.java simultaneously
Also specify the source directory, destination directory and host address of the machine in which server is running in the ClientMain.java(as per your computer). Here we are not specifying source file ,instead a source directory or folder is specifying.So the entire files of source directory will be transferred.
I have been practicing writing java code, my university course is going to cover socket programming and multi-threading.
I am presently just starting to write myself a framework for all multiplayer games I may make in the future, my aim really is simply to practice and understand better and this time, im not using an ide, just sublime text, all new grounds for me, I have a good basic understanding of the subject but I want to be fluent.
import java.net.*;
import java.util.ArrayList;
import java.io.*;
/*SMOOTH THREAD SAFE MULTI CLIENT HANDLING CLASS.
*
*This class will create connection objects when a connection is detected, these connections will run in a separate thread and update an array list in their parent class containing their last sent data
[Code] .....
I have a jFrame and a Java Class. Now i have a path of image in my jFrame which I want to display in java class(Crop2). I created an object in jFrame
Crop2 d=new Crop2();
and then I'm trying to send the data to the class file but it is not working.
I'm working on an assignment right now which involves passing a variable series of numbers to the Server to be sorted into the correct order and returned to the client.
So far I have it connecting to the server and asking for my numbers, and I am entering each number and pressing return, and it is accepting each number individually.
One (smaller I think) problem i'm having is with the client code, specifically the while loop.. I've tried to code it so that when I enter a full stop ('.') the program will stop asking me for more numbers and move on to sending them to the server.. but instead it just crashes giving an error.. heres an example
"Enter a number: 1
Enter a number: 3
Enter a number: 2
Enter a number: 1.
java.lang.NumberFormatException: For input string: "1."
at java.lang.NumberFormatException.forInputString(Num berFormatException.java:65)
[Code] ....
Here's the client code in full
package numberSortprogram;
import java.io.*;
import java.net.ServerSocket;
public class NumSortClient {
public static void main(String[] args) {
InputStreamReader is = new InputStreamReader(System.in);
[Code] ....
The big problem that I have is figuring out how to send the sorted array back to the client..
So, what im trying to get to happen is-
-Client is asked to enter numbers
-Client enters series of numbers into an array
-Array is converted to a string and sent to the server
-String is then split into an array of strings and sorted using compareTo (don't know if this is the best way?)
-Sorted array is sent back to client and displayed.
fyi this is making use of streamsockets..
All of the rest of my code is below:
package numberSortprogram;
import java.io.IOException;
import java.net.*;
import java.util.regex.PatternSyntaxException;
public class NumSortServer {
public static void main(String[] args) {
int serverPort = 4444; // default port
if (args.length == 1 )
[Code] .....
I have two separate java Program that run on the same
computer : Program -1 & Program-2 .
Explain Program-1 :
Name of Program -1 is “InputFrame” that is a simple frame that contain a JTextField and a Button and a JTextArea .
Explain Program 2 : Name of Program-2 is “OutputFrame” that is a simple frame that contain a simple JTextArea that this JTextArea is a Instance object from a class with name of “DisplayFrame” .
This instance object from class of “DisplayFrame” added to frame of “OutputFrame”.Now I want run both Program 1 & 2 simultaneously in the same computer and when I enter a text in JTextField in Program-1 and after click on the Button “OK” that Text Entered in this JTextField In addition to JTextArea in Program-1 display In JTextArea in Program-2 .
I do not want use a share file between two Program-1 and -2 Or DataBase .I want if Program-1 run but Program-2 is not running and i enter a text in JTextFeild in Program-1 , after running Program-2 that Entered Text Displaye in JTextArea in Frame of Program-2 .(Offline Message) .Both Source code of Program-1 and Program-2 is Attached .
My primary question is about which method is the best for having an applet of mine communication with a backend database of mine. In other words, I don't want to try learning a technology that is out of date or not a good fit for my goal. I purchased the O'Reilly title "Java Servlet Programming", but it seems to be very old and out of date (referencing Netscape 4, etc.) and I see a Java RMI O'Reilly title on Amazon, but it was written in 2001.
My basic goal is to allow my applet to have access to a back-end database for reading and writing. I understand that direct Applet to DB (via JDBC) access is a bad idea so my thought is to create a servlet (much like web service for lack of a better term) or an actual web service (RESTful would be my first guess) to broker the requests. I already have a very basic servlet running that has access to my database server so now I want to focus on the best method for making calls from the applet to the servlet but having said that I don't want to go down this road too far if a servlet is not the right tool for the job.
My reading has been leading me to RMI, but as I said, I don't want to focus on that if there is a better option. In a non-Java environment, I'd use a web service (REST, SOAP, etc.) and perhaps that's what I should do here as well and not even bother with a servlet per se and just go with a web service.I know there can be some subjectivity with regard to these choices and I don't need to know what the "best" one is.I don't want to use RMI if it's dead or has been surpassed by something else, for example.
Should I use a servlet? Should I use a web service? My needs are rather modest; query the database, send updates to the database, etc. Nothing too crazy.
I have an application written in Java on the Linux platform. My application will work the following way:
User A will open application. User B will open application.User A will need to send User B a message but without a socket connection.User B will need to send User A a message but without a socket connection.The user should be able to identify the messages sent to each other.If User A reads user B's message the message will no longer be available in the channel of communication.If one user exits their application their message should be removed.User C should not be able to read user A and user B message (This is only via the application design, no real security here).Applications should be able to work on different machines however they will utilize a shared network mount to access files modified by each other.
I do have to note that the messages being sent is rather small and only 1 message is sent from each user, so in that regard I did not want to setup a client/server model to do this using sockets.
Basically I am looking for a similar concept as a message queue but more relevant to my requirements done in Java. What are some good options to use that will address some of my requirements? I have not touched Java in a long time and only have used it for certain usage so I am trying to get an idea of which current technologies are best for what I need.
The following programs exist:
1. I have a java application which accepts bio potential data every second or two and stores it in the database. This is a socket server which accepts this data from multiple clients and spawns a new thread for processing it to store in the db.
2. I have a jsp page on tomcat server which reads historic client data from database (stored by application 1) and displays it on the page.
The socket server program in 1.) above is not running inside of tomcat server.The new requirement now is : Display all of the human data coming in live on the jsp page.Now the problem: I will now need to pass the live data from socket server (which is stand alone) to the jsp which is running on a tomcat server.
Possible solutions:
APPROACH 1: Run the socket server in the tomcat instead of stand alone and store the frequently incoming data in a java object so the jsp can access this object every second and display it on a graph.
PROBLEM : The stand alone java application does not need to be included in a tomcat server except for the fact that the jsp needs access to the live data. Also, I have read that this is not the best way.
APPROACH 2: Expose the stand alone java application as a web service and communicate with the jsp using REST architecture.
PROBLEM : The complication of using this method is that it will not have the flexibility offered by websockets or server sent events (SSE) of auto updating the latest data. The jsp will have to keep polling for new data every one second which is also not a very good option.
I am working on a project with client/server relationship and I want the client to be able to transfer their personal music files over the socket. Every time I attempt to do it the file is created but it is empty.
Server code:
Java Code:
public class Server extends JFrame {
//===============================
// FIELDS
//===============================
// connection essentials
private ServerSocket server;
private Socket connection;
[Code] ....
We have two servlets application running on same server with Java EE 6 with below mention application URL.
Servlet1 Application URL: http://<severname>/*servlet1*
Servlet2 Application URL: http://<severname>/*servlet2*
My question is how to call Servlet2 from Servlet1 with Post method without using server name. May be something like this:
servlet.invoke(servlet2).
I want to make project about java communication with hardware (wiz110sr) via LAN (Rj45). And for example, my hardware have ip address 198.168.0.1 ; port: 1202, connected with my PC(via lan/Rj45). I want show the output (such as numbers and letters) from my hardware in console netbeans.
When I running my code, appear :
" Exception in thread "Thread-0" java.lang.RuntimeException: Uncompilable source code
at mypkg.startListenForTCP$1.run(startListenForTCP.ja va:48)
at java.lang.Thread.run(Thread.java:745)
BUILD SUCCESSFUL (total time: 1 second) "
Here's the code :
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import sun.rmi.runtime.Log;
[Code] .....
Firstly, my code is just a demo of my multiplayer game (2 or more players can play simultaneously) to demonstrate my problem without any extra things. I have successfully implemented peer-to-peer (P2P) communication in my game. Later, I decided to add support for client-server communication (ie a central server which is also a player) in my game. It should be much easier than P2P. Now here is the problem:
Suppose, I have 1 server and some clients (may be 1 or more clients). They all should give the following output:
Starting...
A
B
C
E
F
...
...
Done!
They all give the above output without using multi-thread. But using multi-threading, it gives the above output only when there're 1 server and 1 client. I'm using 2 threads (1 for sending, 1 for receiving) for each Socket. That means, each client has only 2 threads for communication but the server has (2 * totalClients) threads.
I've attached my full test project. So, here I'm only showing my 2 thread classes.
ReceiveThread class:
class ReceiveThread extends Thread {
private ObjectInputStream receiveStream;
private BlockingQueue<Character> queue = new ArrayBlockingQueue<Character>(Common.totalClients);
[Code] ....
Since I've attached my full test project, I'm not showing the other 3 classes. They are ServerMain, ClientMain and Common. If I've 2 clients to be connected, then I get the following output:
Server: (Runs first)
Starting...
A
Client 1 (clientID is 1): (Runs after the server)
Starting...
A
B
B
Client 2 (clientID is 2): (Runs after Client 1)
Starting...
A
They are stuck at there, even no exception. Actually, the server and the clients are stuck at the line try { ch = queue.take(); } if more than 1 client are connected. It seems that all are trying to receive data. But without using the dedicated threads, they all work as expected even for more than 1 client. Why is this behaviour? How to solve it? Note that I have used the same SendThread and ReceiveThread classes by which I have succcessfully implemented P2P communication.
About my attached test project file:
It has 5 small .java files for the classes as stated above. It is currently faulty when using additional threads. You have to change clientID variable for each client (they are described inside). But it works as expected without additional threads. To test it without the additional threads:
Comment " TODO" linesUncomment the single lines just after " TODO" linesComment the additional thread construction lines (4 lines)
Currently, for a workaround, I'm not using the dedicated threads for sending and receiving data only for client-server communication in my multi-player game. But I'm still using these threads for P2P communication. I don't know why it is and how to solve it.This is the attached test project file as described above.
Attached File(s) : Test Project.zip (4.11K)
I want to make a service like Spotify, where I can stream music that I have stored on my computer (in this case server) to my laptop or phone.
* What would be a suitable format for this?
* How would I actually stream it? I want to stream, not download and then play, I want to play the music while downloading.
I have a program thats ran over a network and is multi-player. However whenever I fire any bullets they do not fire on the other clients screen. Here's the code
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
import java.util.*;
public class TankWar {
[Code] ....
I am trying to develop an application which will be showing a TimeSeries graph(related library JFreeChart) displaying network activity related to a particular network interface embedded in a JFrame.I have created a JPopUpMenu which is having containing a list of JMenuItems showing network interfaces as their String values.Menu is popping up correctly
Further I am selecting a JMenuItem related to a particular network interface to show network activity in TimeSeries graph.On selecting a JMenuItem I can see that graph is moving on constantly but not able to see any network activity.
Pasted the code below :
package com.ankit.analyser;
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Window;
import javax.swing.JFrame;
[Code] .....
Further I can see that packetArrived method of PacketListener is not being overridden by class PacketHandler as I am not able to see data packets on console and static list in main class is also empty.
I am learning few concepts in servlets. And i came across this doubt. We used to send data over network using httpsession as below.
HttpSession session = request.getSession();
Object obj = new Object();
session.setAttribute("object", obj);
And get the data in JSP with below code
<%= session.getAttribute("object")%>
However I am not sure whether HTTPSession is serializable or not.
How HTTPSession works?
Suppose you are given a computer with 1GB RAM. The disk of this computer holds a 10GB file containing random numbers. Propose a technique for sorting the file without using the disk or network or virtual memory. Outline your approach, propose an algorithm, and implement the algorithm. What is the algorithmic complexity of your algorithm.
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