Java Solution To Communicate Via Applications On Without Sockets
Oct 6, 2014
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.
I 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
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 )
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 just installed java on my computer because i was getting messages that it was no longer there. And I figured out how to solve my problems on my browsers. but i don't see how to enable java in my applications on the hard drive. in particular, i want to use the database in open office but don't see how to enable it.
I am maintaining an existing Java product (which has a HUGE code-base). I discovered that it is setting (and getting) two of its internal passwords as Java system properties, at no less than 4-5 different places (methods). Now, the problem is, the passwords are being stored as plain text in the Java system properties, and so, the same is visible to external entities, as the application is not using any Java Security Manager. For example, if the application (process) is running on port number 1234, we can run the Java command:
jinfo -sysprops 1234
to view both the passwords as values of the corresponding Java system properties. I wish to ask if there is any remedy to this without changing the existing code-base too much? The desired effect would be to "hide" the two Java system properties (denoting the two passwords) from all external entities.
It may be noted that introducing a Java Security Manager into the application may not be a solution, as if we revoke read permissions from the said two Java system properties using the Java Security Manager, the application codes which read those properties would crash. Same is applicable for storing the passwords in encrypted form, as that would crash all codes within the application which are expecting to read the passwords in clear text form.
To give a bit more context, the said two passwords we are storing as Java system properties are actually passwords to access two key-stores, and Tomcat requires that we store the said two passwords in plain-text format. Any workarounds, such that only Tomcat will be able to see the two passwords as-is, while they will be invisible to all other external entities?
Or, is there any way to place the said passwords in other in-memory locations (like static variables) which only Tomcat can (be made to) read instead of placing them as system properties which is exposed to anyone?
I have a problem with several java applications. When I start them Java wants to connect to the certificate authority, to check if the certificate is still valid and not on a blacklist.
The problem is: my whole internet is behind a password protected proxy. If I open my browser i get a windows with username and password. I enter it and internet in the browser works. But for Java it isn't working, because I see no point, where I can enter the password and username for the proxy. I can enter the proxy ip and port in the java settings, but not the password and username. So I get a error screen from java, telling me, that java could not connect. I can disable the check in the java settings, but I don't wont that.
Is there a way to tell java, that java uses my proxy with my password and username? I already googled this problem and found nothing except tutorials for connecting with proxy in the java code. But these applications are not from me, I can't change the code ...
I can often write a recursive backtracking solution, but don't know how to cache the answers into an appropriate array.
For example:
Java Code:
public static int max(int[] costs, int index, int total, int shares) { if(index >= costs.length) { return total; } int buy = max(costs, index + 1, total - costs[index], shares + 1); // buy one stock int sell = max(costs, index + 1, total + shares * costs[index], 0); // sell all stocks return Math.max(total, Math.max(buy, sell)); // compares between buy, sell, and doing nothing } mh_sh_highlight_all('java');
This is a dynamic programming exercise, but I have no idea what dimensions the dp array should be (I was thinking maybe dp[index][total][shares], but that seemed like overkill). Is this just because my understanding of recursion isn't solid enough or am I missing something else?
This is what the gui looks like at run time. The question is how do I compact it so there is not so much space between the labels and the textArea. I've tried using different numbers on my GridLayout, but not a lot of success.
I use a bluetooth module (dwengo) in combination with a microcontroller (PIC16F877A). I want write a bluetooth client program in java to communicate with the microcontoller. Examples of clients on internet do not work or give errors I cant'n resolve. There is one program ( SampleSPPClient ) that give no errors and shows the bluetooth devices present.
But when I choose my bluetooth module I got an error (Device does not support Simple SPP Service). I think that I have to use an other service of bluetooth but I don't know how to implement. Here is the program I tried to use ....
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:
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..
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());
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 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;
We have this website that is run on two web applications. The first web application hosts the home page and clicking certain links in the home page would forward it to pages of the second web application where certain functionalities can be done. Now, there has been an initiative to redesign the site to have a login page and only logged in users could browse it. This would mean a login page being created in the first app, and when links to the second application are clicked, the pages are supposed to forward to it with the same session of the user that logged in.
We have already creating handling to pass the session from the first app to the second. Logging out from the first application would also invalidate the same user session in the second application. My questions is, is this a bad idea? would it be better to combine the two apps even if it would mean a huge impact?
or is there are better way to do this? like set it in web.xml. I have read that you cannot use two context for it.
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.
I would like users in an application to be able to access and edit their user profiles (Application A). The problem is that the user objects (entities, dao, beans) are handled in a separate application (Application B) which is specifically for managing user accounts. Importing the java sources for App B into App A could be messy and might need configuration of the persistence unit and connection. I'm thinking it would be better to inject an EJB from App B to App A to query the user DB and return the results so a user profile form is rendered in App A.
I know how to inject EJBs within the same application, but I'm not so sure about how it's done across different applications or even if that's the most advisable way to achieve what I want. it's better practice to inject an external EJB into App A or simply import the classes from App B and use those.
@Stateless public class UsersDaoImpl implements UsersDAO { @PersistenceContext private EntityManager em;
I question this as I have not yet succeeded in deploying a working ruleset for use with intranet based applications. I have verified the ruleset is working with external internet java apps so it is being deployed correctly just doesn't steer Intranet based apps to the correct version.
