Sending To All Vs Sending To One Person In Server / Client Program
Apr 17, 2014
I have two programs that I'll post below, one is a Server and the other is a Client. The ChatServer runs once and many clients can run ChatClient from separate computers and talk together in their GUI's. The the client program comes with two buttons, one that's simulates the sending of a message to a single user ; "Send Message To User", and one that just generally sends a message ; "Send Message To All". Although now the Clients on the server seem to be able to selectively send messages to an individual by giving the recipient name, all the clients can see that message, which is not exact what I am aiming for. What I am going for is having the "Send Message To User" button click to send a message to the named user without all other users seeing the message.
Now I have tried thing like having various input output streams and trying to connect those, but no luck. Tried fiddling with having the names arraylist directing the messages to one client versus all but that did not work out either. How I what I would need to do to go about doing this?
I've just recently started playing around with network programming in Java, and I've come up with a simplistic server than can handle multiple clients and return the IP and port each one is connected to (or I'm under the impression that is so). What I've been requested to do as an exercise by one of the programming teachers at my high school (I'm not in a class, this is my own time) is send a message from one client to the other through the ServerSocket so that it may "watch" everything going on. I'm not sure how to go about this at all.
EDIT : now it never seems to go the the else or else if statements...
That is now the main problem. It never, ever, goes past the first if statement, no matter what it is.
EDIT : Okay, I haven't changed a line of code but suddenly not a single if statement is working. They just stopped. The client simply hangs and I can't type anything.
Server
public class Server implements Runnable { Socket clientSocket; Server(Socket clientSocket) { this.clientSocket = clientSocket; } public static void main(String args[]) throws Exception { ServerSocket ssock = new ServerSocket(3480); System.out.println("Listening on port 3480");
I am creating a server that stores application updates. When the client connects the server send the update. The server is sending the file but the file is not complete, i.e, if the file is 317kb,its send 117kb. Below is the code I am using :
import java.io.BufferedInputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.OutputStream; import java.net.ServerSocket; import java.net.Socket; public class TestFileServer {
I am trying to check the integrity in a Bank Transaction that the message sent to the server has not been modified by any malware in the client system. For this I am trying to read the message sent to the server at the client boundary so as that it enters the network as customer with customer intended values. So, firstly I need to check where to I need intercept the message within client boundary. Secondly, Can I intercept the message and read its contents using Java?
I want to check what my Online Banking Server( Leta Say Bank of America) receives if I ask to transfer amount $100 to Account A . I assume that there is a malware in client system that changes recipient to B,$10000. My aplicaion which I intend to design, shoudl inform the user that the integrity of the message is compromised and should give the option to the user to abort it. plan to track what message is being sent from client to server. This I want to achieve by reading the message from client at the last point before it leaves the client and enter the network.
I have to write a client and server class for a UDP protocol sending integer numbers by UDP packets. So far i have this;
Client Code:
import java.io.*; import java.net.*; class UDPClient { public static void main(String args[]) throws Exception { BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
[Code] ....
But i now need to change this so that:
The client;
1. Reads an integer from keyboard input and stores its value in a UDP packet. // byte[] send = ByteBuffer.allocate(4).putInt(num).array(); ???
2. Sends the UDP packet to the server, on port number 1999;
3. Listens for UDP packets from the server (until it receives a packet with a non-positive number; see step (b) below). While listening:
(a) Once it receives a UDP packet from the server, it subtracts 2 from the integer value num contained in it. // int num = ByteBuffer.wrap(receive).getInt(); ??? (b) Checks the integer value num: if the value is greater than 0 (num>0) then the client stores it in a new UDP packet and sends the packet to the server; otherwise (num<=0) the client terminates.
The Server;
1. Listens on port 1999;
2. For each UDP packet it receives from a client: (a) extracts the integer value n contained in it; (b) decreases the value of n by 2; (c) sends back to the client a UDP packet containing the new value of n.
I'm making a class in Android that takes a photo, list a photos in Listview, and then sends them all to server. I'm stuck on listing them. How to send them all to server.
At first, oracle change this site a lot. I logged into this site after a long time and I was amazed to see the new changes. Moving onto the the question.
I am developing a spring mvc web application. The problem is when I send email, let say to more than 4 person, the program hangs for a while. Some friend told me to use thread pool to solve this. What is the general practice for handling this kind of situation?
I have to develop a code in parallel which is implemented in sequential yet. How to add the server client relation in the program so that work can be divided into multiple clients.
So i wrote this text to try and create a simple chat program that does the following: Prepend names to messages, announce entrance and exit of chat, display user list, and share a whiteboard.So far the Server seems to be working but the Chat Client is throwing errors at me left and right..
CURRENT ERROR: Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:Windowssystem32>cd.. C:Windows>cd.. C:>Usersjaydesktopchat 'Usersjaydesktopchat' is not recognized as an internal or external command, operable program or batch file.
I've been provided a code skeleton for what must be done, but despite my best efforts to make things work, I'm coming up dry (obviously, due to a lack of knowledge.) One thing that might work is if I knew how to debug this type of application, line-by-line, to see exactly what is going on. Obviously, it's easy enough to debug the client part, but moving over to the server part, I haven't been able to figure that out (I'm using Eclipse.)
I am currently writing two java classes (client and server). The client takes an input number form keyboard and sends it to the server. The server then multiplies this number by two and sends it back to the client. The numbers should also be printed to screen along the way, for example if I input the number 3 I should get
"From Client: 3" "From Server: 6"
They should continuously do this unless a negative number is received by the client, say for example the number -3 is sent to the server and it returns -6.
The code I have for the two classes so far is:
import java.io.*; import java.net.*; import java.nio.ByteBuffer; import java.util.Scanner; class Client { public static void main(String args[]) throws Exception { DatagramSocket clientSocket = new DatagramSocket();
[Code] .....
Currently, when I run the program all I get is an output of the number first entered. I am aware it requires a loop but I don't know where and what the condition should be.
Also if I wanted to adapt this so that it would take the integer from client and subtract two at the server and return to client who sends back to server to keep subtracting two unless it reaches a negative number at which point the client will terminate the program - how might I do this.
I do realise there needs to be a while loop in the above code, but I wanted to test it sent the number from client to server and its not doing it. All I get is a print screen of 'enter number' and then the number I enter.
I had some questions about a theoretical java program. Say you had a java program on a linux server/pc that referenced a folder on that server. And say you had a Client PC (Windows) that had a share folder to that java program.
If that windows client PC tried to run the program would it run (with a GUI if it had one) and would the main directory of the java program still be on the linux server or would it be on the windows computer since that is the computer that is running the program?
Basically I have a program I am trying to find the best way to run it remotely on a windows computer but it references files on the linux server it is located at and needs to put files it creates there as well. I am just trying to make sure I understand my theory here on how the program will run if it IS run remotely.
My overall goal is to create a server that can receive a message from a client and send an automatic reply in captial letters..As well as having the incoming messages decoded to display the header information..The server also needs to save a log of incoming and outgoing commutations..The client needs to be able to attacha text or JPG file and be able to coummucnate with the client.Okay this is what i have so far
I really need them to be able to communicate with each other with messages i am struggling making that work as so far they can talk only to themselves the message aren't getting sent between them, let alone adding the other feutures.
I have a server with a handful of php services. I communicate with these services by creating connections from java code. The services currently respond with XML, but that can be changed if an alternative way can improve performance.
One of the things I need to do is send varying sized payload (some large) to one of the services. My current plan is to create an xml file in java and perform a POST request with the XML as the payload. I am using an XML because the data is very structured.
From a performance point of view, would it be better to send the XML as a file or just as text? Also, is there a better way to send this data? These services will eventually be used by an android app, where performance and minimizing the size of the data packages will be extremely important.
I did this using ArrayList<String> and my tests worked. Meaning I was able to read the strings in a different class through my constructor. However I want to use a string array because it will be easier to handle when I finish the program. I will send each players poker hand in and figure out who is the winner instead of putting it all onto a ArrayList and having to iterate through it. However whenever I did my check I am just printing null.
PokerFile class
void separateHands(String cards) { //ArrayList<String>playerOne = new ArrayList<String>(); //ArrayList<String>playerTwo = new ArrayList<String>(); String[] playerOne = new String[10]; String[] playerTwo = new String[10];
[Code] .....
ignore the boolean methods I was just building the structure of the program. The print file is what is outputting this:
null null null null null null
public class WinningHand extends PokerFile { //ArrayList<String> p1 = new ArrayList<String>(); //ArrayList<String> p2 = new ArrayList<String>(); String[] p1 = new String[6]; String[] p2 = new String[6]; WinningHand(String[] p1,String[] p2)
New to SMSLib. I checked some samples and docs but did not get any ref/poc wherein I can send SMS with following set-up.
1. I want to send SMS from PC which is connected to internet in office network, where I am using proxy settings to connect to internet.(Basically office PC used in LAN environment)
2. I am not sure how to set the Modem settings in this scenario.
3. What i want - want to test SMS functionality in office environment and would like to send SMS to android based mobile using SMSLib library.
4. I have done SMSLib set-up on my PC and have all the required jars/dlls placed at proper location. So no issues related with set-up. Set-up is on windows platform.
5. I have written sample POC by referring some blogs/SMSLib docs. But as mentioned in points 1 and 2 above, am not getting how to write the code.
I am trying send email .So I have downloaded javaEE and javamail jar files and added buildpath.And wrote this code below .But I am getting this exception.
I am new to java (been Reading for 2 days now), and have almost no knowledge on programming (I am a Mechanical Engineer).The problem I have is that I have to upload 5,000 files to a web page (each one is name B001400XXXX.pdf in consecutive order).I have managed to access the web page and select a few form elements using watij, but I am having a hard time sending my pdf file to the server. This is what I have so far:
Java Code: import org.watij.webspec.dsl.WebSpec; public class NewClass { public static void main(String[] args) {
I need to send a byte array across a network. I know how to do this. (server->client)
byte[] myArray = new byte[]{0,1,2,3,4,5,6,7,8,9}; DataOutputStream.write(myArray);
... and I know how to receive it.
byte[] myArray = new byte[10]; DataInputStream.read(myArray);
When I send over one of these arrays, it ends up stopping storing values in the array when only about half the array is received, even though the array is sent from the server all at once. This results in the receiver's array, in this case, being something like {1,2,3,4,0,0,0,0,0,0}.
I can easily solve this - and already have - by simply adding a loop onto it and waiting for the bytes to all be received, as the method returns the amount of bytes actually read.
I am simply wondering if there is a better solution to this, as the current solution isn't that elegant. Did I do something wrong to cause only a part of the array to be sent first? Would it be better to use DataInputStream.readByte() to read off the bytes one by one rather than an array at once, and then store them in an array afterward? Would this cause a performance decrease as each byte is read individually? (I'm sending an array of several million bytes)
Say I was to make a computer game, the first person to play the game would have a joinable game and would then be the server, and anyone joining in would be the client and the server was updated with JSON data of the clients computer game, and the server would then update each client of each characters new data using JSON, I would need fast multi threaded connection handling with minimum overhead, Is there a specific way to do this? or are there many?
I have realized there are a few ways to send and receive data using UDP and while experimenting I have also found its quite hard to synchronise.
Do I have a connection listening until there is data to be sent and then switched back to listening?
Do I have the server listening for a microsecond and then checking to see of there's anything to send for a microsecond continuously?
Do I have multiple connections for sending and receiving
Do I create new connections for each new and individual packets to be sent and received dynamically on a thread?
What is the optimum most effective way and do my examples reflect much understanding at all? my resent attempts create new problems and rather than re invent the wheel I would like to know what is normally done.
I have a simple class, called InputManager, which has methods that communicate with another class DatabaseManager which has access to Database which is actually object that contains information about actual database.
My JFrame has Navigation class (extends JPanel). There I put all needed JButtons, JLists and so on.. This class has instance of InputManager and when user interacts with GUI components inside of it, Navigation calls InputManager methods, it then analyses the call and calls needed methods on DeviceManager, which then sends queries to Database and etc.
The problem is, that at the beginning (when user runs a program), I want to get information (which is actually values for my GUI components ) from Database. It could, for example, create another DatabaseManager and connect to the Database to get information, but it is okay to have two objects?
I was also thinking about sending same DatabaseManager object through InputManager to Navigation, but it seems strange for me to have two objects, which can interact with each other in both directions(Class A has instance of Class B, and Class B has instance of Class A). Is there anything bad this can do?
Also what I noticed that it seems odd that GUI class would have to get information from database. (Logic in GUI class).
i am having a below piece of code in my worker thread. In my output i am getting xml records from the database. I'm sending this output to a input stream & finally to a sax parser.My query is, before sending to the parser i need to store the input stream in buffer. The buffer should store 1000 records. For every 1000 records the parser should be called from buffer.
while (orset.next()) { output = orset.getString("xmlrecord"); writeCount++; InputStream in = new ByteArrayInputStream(output.getBytes("UTF-8")); InputStream inputStream = new ByteArrayInputStream(output.getBytes("UTF-8")); Reader reader = new InputStreamReader(inputStream,"UTF-8");
