Client Server Application Problem ;

Data is not received to two clients simultaneously . Data is received correctly to first connected client only

Shahid,
what you are listing is VI Server access. This is not intende for data transfer but for "remote control".
Do you have dedicated LV applications which should "talk to each other" or do you use web interface (Web Publishing Tool)?
Can you post the code for the server/client?
Norbert
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.

Similar Messages

Problem using the File Dialog Box in a Client/Server application

I am developping a client-server application using Labview 5.1 . The application on the server acquires data from some instruments and saves it on file, while the application on the clients displayes such acquired data. For doing this I call some routines on the server via the "Open Application vi" (remote connection). All goes well except when I open on the server the "File Dialog Box vi" : in this case the application on the clients is blocked (is blocked the execution of the called vi on the server). Only when
the File Dialog Box on the server is closed, the execution of the called vi on the server starts again.
I need to use the File Dialog Box on the server, but I don' t want to stop at the same time
the clients !!
I need help for resolving such problem.
Many thanks in advance !!!

Hi!
waldemar.hersacher wrote:
"It seems that the VIs called by the clients are running in the user interface thread.
A call to the file dialog box will call a modal system dialog. So LV can't go on executing VIs in the user interface thread."
Are you sure? I think, that File Dialog, called by LabVIEW File Dialog from Advanced File Functions Palette doesn't blocking any cycles in subVI, which running in UI Thread. Look in my old example (that was prepared for other topic, but may be good for this topic too).
2 linus:
I think, you must a little bit reorganize you application for to do this. You must put your File Dialog into separated cycle. This cycle, of course, will be blocked when File Dialog appear on the screen. But other cy
cle, which responsible for visualization will run continuosly at the same time...
Attachments:
no_block_with_file_open_dialog.zip ‏42 KB

HELP - problem in running SSLSocket client/server application

Hi,
I want to create a SSLSocket based client/server application for this i have used EchoServer.Java and EchoClient.Java files. Both files are successfully compiled and when i ran EchoServer it throws an exception "Server certificate not found".
I want to make a complete auto-controlled client/server application which will automatically gets certificate and all configuration itself from program because i will use both client and server application in as a servlet part.
I did as per following instructions:
-Create a keystore to hold the private and public keys for the server. e.g.
keytool -genkey -keystore mykeystore -alias "myalias" -keypass "mysecret"
-Export the X509 certificate from this store
keytool -export -alias "myalias" -keystore mykeystore -file mycertfile.cer
-Import this into a trustStore for the client
keytool -import -alias "myalias" -keystore mytruststore -file mycertfile.cer
-Run the server using the keystore
java -Djavax.net.ssl.keyStore=mykeystore -Djavax.net.ssl.keyStorePassword="mysecret" EchoServer
-Run the client using the truststore
java -Djavax.net.ssl.trustStore=mytruststore -Djavax.net.ssl.trustStorePassword="mysecret" EchoClient localhost
EchoServer.Java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
import javax.net.ssl.SSLServerSocket;
import javax.net.ssl.SSLServerSocketFactory;
public class EchoServer {
public static int MYECHOPORT = 8189;
public static void main(String argv[]) {
try {
SSLServerSocketFactory factory =
(SSLServerSocketFactory) SSLServerSocketFactory.getDefault();
SSLServerSocket sslSocket =
(SSLServerSocket) factory.createServerSocket(MYECHOPORT);
while (true) {
Socket incoming = sslSocket.accept();
new SocketHandler(incoming).start();
} catch (IOException e) {
e.printStackTrace();
System.exit(30);
class SocketHandler extends Thread {
Socket incoming;
SocketHandler(Socket incoming) {
this.incoming = incoming;
public void run() {
try {
BufferedReader reader =
new BufferedReader(new InputStreamReader(incoming.getInputStream()));
PrintStream out =
new PrintStream(incoming.getOutputStream());
boolean done = false;
while (!done) {
String str = reader.readLine();
if (str == null)
done = true;
else {
System.out.println("Read from client: " + str);
out.println("Echo: " + str);
if (str.trim().equals("BYE"))
done = true;
incoming.close();
} catch (IOException e) {
e.printStackTrace();
EchoClient.Java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
public class EchoClient {
public EchoClient(){}
public static final int MYECHOPORT = 8189;
public static void main(String[] args) {
/*if (args.length != 1) {
System.err.println("Usage: Client address");
System.exit(1);
String sAddress="localhost";
InetAddress address = null;
try {
//address = InetAddress.getByName(args[0]);
address = InetAddress.getByName(sAddress);
} catch (UnknownHostException e) {
e.printStackTrace();
System.exit(2);
Socket sock = null;
try {
sock = new Socket(address, MYECHOPORT);
} catch (IOException e) {
e.printStackTrace();
System.exit(3);
SSLSocketFactory factory =
(SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket sslSocket = null;
try {
sslSocket =
(SSLSocket) factory.createSocket(sock, args[0], MYECHOPORT, true);
} catch (IOException e) {
e.printStackTrace();
System.exit(3);
BufferedReader reader = null;
PrintStream out = null;
try {
reader = new BufferedReader(new InputStreamReader(sslSocket.getInputStream()));
out = new PrintStream(sslSocket.getOutputStream());
} catch (IOException e) {
e.printStackTrace();
System.exit(6);
String line = null;
try {
// Just send a goodbye message, for testing
out.println("BYE");
line = reader.readLine();
} catch (IOException e) {
e.printStackTrace();
System.exit(6);
System.out.println(line);
System.exit(0);
} // Client
Can anybody will please help me to solve my problem i am using JDK1.4.2_07
Thanks in advance.

Hi,
I want to create a SSLSocket based client/server application for this i have used EchoServer.Java and EchoClient.Java files. Both files are successfully compiled and when i ran EchoServer it throws an exception "Server certificate not found".
I want to make a complete auto-controlled client/server application which will automatically gets certificate and all configuration itself from program because i will use both client and server application in as a servlet part.
I did as per following instructions:
-Create a keystore to hold the private and public keys for the server. e.g.
keytool -genkey -keystore mykeystore -alias "myalias" -keypass "mysecret"
-Export the X509 certificate from this store
keytool -export -alias "myalias" -keystore mykeystore -file mycertfile.cer
-Import this into a trustStore for the client
keytool -import -alias "myalias" -keystore mytruststore -file mycertfile.cer
-Run the server using the keystore
java -Djavax.net.ssl.keyStore=mykeystore -Djavax.net.ssl.keyStorePassword="mysecret" EchoServer
-Run the client using the truststore
java -Djavax.net.ssl.trustStore=mytruststore -Djavax.net.ssl.trustStorePassword="mysecret" EchoClient localhost
EchoServer.Java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
import javax.net.ssl.SSLServerSocket;
import javax.net.ssl.SSLServerSocketFactory;
public class EchoServer {
public static int MYECHOPORT = 8189;
public static void main(String argv[]) {
try {
SSLServerSocketFactory factory =
(SSLServerSocketFactory) SSLServerSocketFactory.getDefault();
SSLServerSocket sslSocket =
(SSLServerSocket) factory.createServerSocket(MYECHOPORT);
while (true) {
Socket incoming = sslSocket.accept();
new SocketHandler(incoming).start();
} catch (IOException e) {
e.printStackTrace();
System.exit(30);
class SocketHandler extends Thread {
Socket incoming;
SocketHandler(Socket incoming) {
this.incoming = incoming;
public void run() {
try {
BufferedReader reader =
new BufferedReader(new InputStreamReader(incoming.getInputStream()));
PrintStream out =
new PrintStream(incoming.getOutputStream());
boolean done = false;
while (!done) {
String str = reader.readLine();
if (str == null)
done = true;
else {
System.out.println("Read from client: " + str);
out.println("Echo: " + str);
if (str.trim().equals("BYE"))
done = true;
incoming.close();
} catch (IOException e) {
e.printStackTrace();
EchoClient.Java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
public class EchoClient {
public EchoClient(){}
public static final int MYECHOPORT = 8189;
public static void main(String[] args) {
/*if (args.length != 1) {
System.err.println("Usage: Client address");
System.exit(1);
String sAddress="localhost";
InetAddress address = null;
try {
//address = InetAddress.getByName(args[0]);
address = InetAddress.getByName(sAddress);
} catch (UnknownHostException e) {
e.printStackTrace();
System.exit(2);
Socket sock = null;
try {
sock = new Socket(address, MYECHOPORT);
} catch (IOException e) {
e.printStackTrace();
System.exit(3);
SSLSocketFactory factory =
(SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket sslSocket = null;
try {
sslSocket =
(SSLSocket) factory.createSocket(sock, args[0], MYECHOPORT, true);
} catch (IOException e) {
e.printStackTrace();
System.exit(3);
BufferedReader reader = null;
PrintStream out = null;
try {
reader = new BufferedReader(new InputStreamReader(sslSocket.getInputStream()));
out = new PrintStream(sslSocket.getOutputStream());
} catch (IOException e) {
e.printStackTrace();
System.exit(6);
String line = null;
try {
// Just send a goodbye message, for testing
out.println("BYE");
line = reader.readLine();
} catch (IOException e) {
e.printStackTrace();
System.exit(6);
System.out.println(line);
System.exit(0);
} // Client
Can anybody will please help me to solve my problem i am using JDK1.4.2_07
Thanks in advance.

How to validate a server in client-server application

I am considering a client server application for a masters project. One of the core requirements for this application would be to ensure that the server could not be replaced. This would be easy to do using public/private keys. The client creates a message and encrypts using servers public key, then sends to the server. The server decrypts, processes, creates response, and encrypts using its private key. This works, however the public and private keys need to be in the source code. It looks like keystores may fix that problem, however the password to the key store would then be required. For this application to be usefull, I need to find a way to embed a password or encryption key in a .classfile in a way that it can not be retrieved by decompiling or parsing for strings. Anyone have ideas on how this could be done, or a different method I could use to guarantee that the response coming from a server process is from my server program and not a fake program?

More detail. The program is a network license server (not web based). We need a simple license server for internal use, so that we can track usage and limit concurrent users for custom software. We also need some security so that people can not take the software home and use it. We have looked at commercial applications, however they are very expensive and we can not justify the cost since this is for internal software. There are 3 main pieces to a license server, the client libraries, the server, and the key generator. For the license server to be usefull, it should be impossible (or very very difficult) for someone to generate their own keys and add them to the license server. It should also be very difficult for them to create a fake license server that will grant licenses to clients without needing keys. If public/private key encryption is used, then the client would need to know the servers public key and their private key. These keys would need to be compiled into the program, stored in a key store, or looked up at run time from some other resource. The server would need to know its private key, and the clients public key. Since this is internal software, we can limit access to the server software, so it would be ok to compile the keys into the code (not ideal but secure enough for out use). However if I use this program as my Masters project, I would need to figure out a better way to secure it. The generic problem is how to give someone two programs that talk to each other, and be able to ensure that they do not fake one of the programs?

Client Server Application with images or icons

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

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

Writng-Reading stream through client-server application

I am developing a client-server application which is the client sends a sentence to the server and the server will convert the sentence from small letters to all capital letters. The problem is when the sentence send by the client contains special character such as Registered Trade Mark or Copyright , the server receive the sentence but the special character has changed to undefined symbol. After the server do the conversion process, the server couldn't send back the sentence because of the undefined symbol. It will make the system hangs.
I use socket connection to do the process. The system use DataOutputStream object to pass the sentence . The source code is as below:
Socket clientSocket = new Socket("localhost", 111);
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
sentence = "Stomach-Comfort is the all-natural alternative to over-the-counter products, such as Tums�, Rolaids� and Pepcid AC�.";
outToServer.writeUTF(sentence + '\n');
modifiedSentence = inFromServer.readLine();
System.out.println("FROM SERVER: " + modifiedSentence);
Any body can help me?

Well, I think that this would work but I haven't tried it, but you could evaluate the numerical value of each
character and see if it falls within the range of ASCII fields that you want to convert.
If not don't convert it.
So for example,
for each char in your stream:
1) get a char's numerical value
2) If between 97-122 decimal
convert to the capital (forgot the exact method name)
3) else
keep value as it is.

Client server application using CORBA

Hi
I have a basic client server application running using CORBA/idl where the client starts up and the server says hello back to the client. I have figured out the basics but would like some help with these small problems.
When I start the client, the server says hello. Thats OK. Now I want the client to start a simple java app (called c:\test.java - it works) that I created before. How?
The next bit is when I close down the app "test" that I start, I want the server to realise that its closing and simply say goodbye on the client. How?
If anybody can help me, I'd appreciate it.
Thanks for your time,
Shaun

hi,
to my knowledge, you will have to define a method in idl file and in your client, which server invocates(saying good bye etc) before shutting down..
ls.

Client/server application (Help me)

I have a client server application.In the client part i send data to the server and the server receive data. After receiveing data server also send some data but the client can't capture data. Anyone please tell me what is the problem?
I am giving the sample code here......
I am thinking actually the problem is in the client side.......
Server
out = new DataOutputStream(client.getOutputStream());
input = this.client.getInputStream();
byte[] data=new byte[input.available()];
input.read(data);
byte[] sdata=new byte[3];
sdata[0]=1;
sdata[1]=2;
sdata[2]=3;
out.write(sdata);
Client
How can i implement my client to send and receive at a time??

Thanks all of u.
I have solved the problem.
Now i have another problem.In the Client side I have used DataOutput
Stream(for sending) and InputStream(for receiving).
With the InputStream i am capturing data by this way.....
int dataSize=is.available();
int kkk=0;
boolean hasSize=true;
while (kkk<=0) {
dataSize = is.available();
         if (dataSize != 0 && hasSize) {
                      byte[] dat = new byte[dataSize];
                      is.read(dat);
                       String s = new String(dat);
                       System.out.println("Capture:" + s);
                       System.out.println("data ssss: "+dataSize);
                       hasSize=false;
                       kkk=9;
                   }//End of if
}//End of while
                 Here is the problem. If I am sending from the server data size less 4000 byte then the client can easily capture the data. But when i am sending the data which is very very large such as 70,000 bytes then it creates a problem.
My target is simple. I want to capture the whole data that is send by the server . then want to keep the data in a byte array which size will depend upon the receiving data.
How can i do that??

Advanced Client Server Application

Hi friends .I'm working on a client server project.In this project I must use two OBJECTOUTPUTSTREAM and OBJECTINPUTSTREAM.But in the program one of them lock the program.
This code a part of from my code.
input1 and input2 a ObjectInputStream.
There are two serversocket in the server side.
Client side got two socket and connected server's two sockets.
Sockets had an objectoutputstream and an objectinputstream.
This project about a game .But players can talk to each other.
input1 send the game move to another player.
input2 send the chat message to anoyher player.
But program always wait the input1 after wait input2.As soon as one of the player moves or seend message another side must take it same time
I can't do this.
do{
move=*this*.input1.read();
// this wake for move and lock the program here.program doesn't go down.IT'IS A PROBLEM
message=(String)*this*.inputi2.readObject();
}*while*(!str.equalsIgnoreCase("Kapat"));
I thought very much about it.I think I must use a thing lile listener whitch run as soon as objectoutput write to input.
I'm waiting for your help.If you show a sample code about this subject I pleased very much.
Good luck everone.Herkese iyi �anslar.this explanation isn'about code and it's my own language.
TÜRKÇE
�nsan�n ana dili gibisi yok.Bu aç�klamay� Ba�taki ingilizcede sonra yapt��m için bu dili bu güne kadar geli�tirip gelen tüm türk milletinden özür diliyorum.Amac�m istedi�ime ula�mak ve bu siteyi ziyeret edenlerin % 99 ingilizce kulland�� için böyle yapmak zorunda kald�m.Kusuruma lütfen bakmay�n.
K�sace özetlemek gerekirse uygulamamda Farkl� socketler üzerinden birbirine ba�l� 2 OBJECTINPUTSTREAM ve OBJECTOUTPUTSTREAM var
bunlar�n ikisindende kar��l�kl� ver aktar�yorum .biri oyun hamlesi ta��mak di�eride mesaj ta��mak için.Ama bunlardan biri program� blokluyor di�eride orogram inemiyor.Bu sorunu çözmeliyim.
do{
move=*this*.input1.read();
// Hamleyi beklemeye ba�lad��zaman bir mesaj gelince buraya inmiyor illaki hamleyi bekliyor.
//Hamle geldikten sonrada bu sefer mesaj� bekliyor hamleyi alm�yorr.Bu sorunu halletmem laz�m.
message=(String)*this*.inputi2.readObject();
}*while*(!str.equalsIgnoreCase("Kapat"));
Listener gibi bir �ey kullan�rsam sorun çzülür san�r�m.Yard�mc� olursan�z minnettar olurum.

I'll go further than that. I'd say that these days, any time you have any kind of client/server application, the first question you should ask is, is there any pressing reason why we can't just use a web server for the server do all communication over HTTP using a textual serialization mechanism like XML and preferably using REST?
The documentation and infrastructure for this stuff is so extensive these days, and the potential for repurposing is so great, that going any other way without a good reason is a waste of effort. Even if HTTP/REST/XML isn't an exact fit, it can still be worth it (at least for prototyping) just for the convenience.

Servlet in client/server application?

hi,
I am planing to make a client server application( SWING & an OODB), would it be clever to use servlet ( not httpservlet) as midle tier framework?
If yes , what are the benefits?
Thanks.

thanks for responding
actually my client don't wanna run a separate server application on the hosting machine as it costs too much, so thats why i think there is no other way to achieve the task rather than using servlets.
please do help me or atleast give me a suggestion. actually i'm developing an internet messenger application. i have developed it using client/server application model in which both (the swing client and the server) uses java sockets to communicate with each other. but now i want to develop the server side of the messenger as servlets. but as far as i know the servlets follow the request/response model. if i follow that model i have to use some sort of client pull after certain amount of time say after five or ten seconds, and this approach does not fulfill my requirements as it would slow the performance if there are hundreds of clients calling the servlet every 5 seconds. thus i want to create persisted connections between the client and the servlet which last for the life time of the user's session. also it is important for the data integrity of the application, so please help me in this matter as i have no other source of guidence in this meany world. i hope you will certainely help me in this matter. please mention that if there are any drawbacks of my approach i mean the persisted connections.
thanks you a lot
Best reagrds
Imran Sarwar.

Should i use secure sockets for my whole client/server application?

Hi,
I have a client server application, and I want to ensure that the login process is secure (i.e. use secure sockets). but I dont know how to switch back to a normal socket once that is done.
So I am left thinking that i should just use SSL for my whole application, which can last pretty long. But I would rather not. Is there any other way of doing this?
or should I just encrypt the login info using MD5 or something like that, then send it over an unsecure socket?
thanks!

Hey,
Are you sure you haven't confused JGSS for JSSE?
Imagine you have a client-server system and you sometimes want data sent over the wire to be encrypted... JGSS offers you this flexibility; if you a encrypted transmission, run ift through JGSS before transmitting it; if you don't want an encrypted transmission, bypass JGSS and just send the transmission.
The benefit is the security (encryption) isn't hard-wired into you communications protocol i.e. TLS. JGSS has nothing to do with connections it is just protocol for securing messages, not sending them.
You would need to establish the secure context but this could be done at startup and persist for the duration of you applicaiton invocation. You perhaps might need to implement a mechanism to identify encrypted messages on the receiving peer (so it knows to attempt decryption).
Admittedly, kerberos seems like one of those 'inside-joke' things. I've come to realise if you don't have some sort of kerberos realm/server against which to authenticate - you need to swap it out as the underlying mechanism. How this is done I'm not sure yet, but I intend to find out today....further down the rabbit hole I go!
If I discover anything helpful, I will let you know.
Warm regards,
D

Client/server application under development

Hi there,
I've been working on a client/server application that includes chat and whiteboard features. In terms of how the client app communicates with the server app, my initial thought was to just go with xml, until I reached a snag. Everything about chat and almost everything that is accomplished on the whiteboard can be expressed in terms of text or character data; which what makes xml a good candidate for moving the data back and forth from client to server. However, there's one part of the whiteboard feature that can't be converted to just text. The whiteboard has an ImageTool. With it you can select an image (gif,jpg) from your harddrive and load it into the whiteboard. An image is binary data and simply cannot be put into an xml file for transport. At least, that's my understanding. Am I wrong about this?
So, this poses the questions: "How do other similar applications like MSN Messenger move images around? If they're not using xml as there medium, what are they using? Just plain sockets without any structured medium like xml?"
Please advise,
Alan

You could always Base64 encode the image file content and then put the Base64 in XML.
I am in the middle of a client-server project and I use XStream ( http://xstream.codehaus.org/ ) to convert Objects to XML automatically. I don't have to do any explicit encoding - XStream does it all for me.

Can i use forms 9i or 10g for client/server applications

Right now, we are using oracle 9i DB and developer suite 10g. I have to build a client/server application. In one of the OTN articles, it says that from forms 9i onwards, it's not supporting client/server applications. Do i have to use 6i for this.
Thank You.
Sree.

That's right. Only web deployment is support from 9i onwards. Bad decision since Oracle seems to ignore their customer's view

Are there any Client/Server Application (using sockets) design patterns?

Hi,
The title of the post nearly says it all. I am searching for different design patterns related with the development of a client/server application. I understand that there must be any different ways on how a client/server application can be developed.
Regards,
Sim085
Disclaimer:
When I enter in the Socket forum on this site I recieve this message "Thank you for any participation in this forum. Due to a lack of relevant activity, we have decided to archive this forum on June 16, 2006. For future posts on this topic, we suggest you use the Networking forum" and I am not allowed to create a new post! However I can see posts done yesterday! All i did is add the forum in 'my forums'. Does this happen to you people as well?

Hi Sim085...How are you?
So look this:
http://forum.java.sun.com/thread.jspa?threadID=5148926&tstart=75
I don�t know if is what you want...but I hope in this^^
Ok man...If you have one example for help you is better.
[ ]

Need HELP in JAVA ( client /server application )

hi there ,
I need the following codes in java for my client/server application . which i can use to perform certain function on another computer on LAN. This is part of my semester project . I would really appreciate if any one can help me
->Open/close the CD-ROM once or in intervals (specified in seconds).
->Swap mouse buttons the right mouse button gets the left mouse button's functions and vice versa.
->Start optional application.
->Play optional sound-file.
->Point the mouse to optional coordinates.
->Shutdown the system, logoff the user etc.
->Mouse can be controlled on the target computer with remote mouse.
->Keys (letters) on the keyboard can be disabled.
->Increase and decrease the sound-volume.
->Listen for keystrokes and send them back to you!
I would really appreciate if some1 can help me find these codes in java
thanx
Alamzaib Shafi
[email protected]

Dude, if you did your own homework once in a while you'd be able to handle your own semester project. I hope you fail your class and get kicked out of the program. One less idiot with a diploma competing with us hackers for the tech jobs.
You are indeed a most worthy recipient of my unemployed angst.

Client Server Application Problem ;

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