Client server protocol book

Hi, i want to create a program with applet clients communicating each other by a server. I'm looking for a book about a protocol for this purpuse. Thanks

No recommendations, but note that you're dealing with a lot of parts:
1) Java generally
2) Java applets in particular
3) the HTTP protocol
4) server-side programming
5) (if you feel it's necessary) client/server design in general
There will be books on all of these. The more you know in general is a good thing, but I suspect that you can skip (5), get just a brief overview of (3), make sure you know (1), and read a tutorial on this site for (2). The trickier part will probably be (4).

Similar Messages

Client/server model and avoiding a registry lookup

Sorry if this question has been asked/answered before - I searched the forums and could not find the answer to my quesiton.
I am using RMI to model a fairly vanilla client/server protocol. Client to server communctions are no problem (yet :-)) . The problem is, that sometimes I want the server to initiate communcations to the client (I guess the client would be acting as the 'server' in those instances although the client is the one that makes the initial connection) Is there any way to do this without the server having to bind the client in the client's remote registry? That would require a open port and I want to avoid that for people who are behind firewalls. I was thinking the client could pass an instance of itself, or an instance of a bound stub, and as long as it implemented 'Remote' then it should be OK. I don't have a problem setting up a registry client side, but if I pass an instance of client that is either registry bound or unbound, as long as it implements Remote, (or rather an interface that extends Remote) will the server make remote calls on the client object?
Message was edited by:
SunDog

It's done all the time. What you're looking for is called "callback." Sun has a tutorial.
One note: Calling the client requires the client to open a port for communication. This happens when the client exports the remote object.

Looking for a client/server that supports multiple protocol and delivery

Hi all, I don't know if this the right place to ask my question,here it goes.
I am looking to develop a client-server that supports multiple protocols such as HTTP, HTTPS etc. I am looking for a framework( i don't know if that is correct or I need some kind of web-service (soap etc)) that would manage connection, security etc. I would like to like to devote most of my time in developing business objects with multiple delivery mechanism such as sending serilized java objects, xml message or soap message, or in some case JMS message as well. So I need a client server that can come in via TCP/IP or HTTP or anyother industry standard protocol and I should be able to service him with pub/sub model and also request/response model as well.
I don't know if I had explained what I need, I would like to know what technologies I should be evaluating and which direction I should be heading... Also the server I'm developing should be free of Java constraints if needed...
Also this service is not webbased service as now but if need arises I should have a flexibilty to make them web enabled in future. Also I would like to work with open source webservers or appservers if I need

Inxsible wrote:I installed i3 - along with the i3status - which I still have to figure out. I am liking what I see as of now. It reminds me of wmii -- when I used it way back when. However I do not like the title bar. I would much rather prefer a 1 px border around the focused window.
"i3 was created because wmii, our favorite window manager at the time, didn't provide some features we wanted (multi-monitor done right, for example), had some bugs, didn't progress since quite some time and wasn't easy to hack at all (source code comments/documentation completely lacking). Still, we think the wmii developers and contributors did a great job. Thank you for inspiring us to create i3. "
To change the border of the current client, you can use bn to use the normal border (including window title), bp to use a 1-pixel border (no window title) and bb to make the client borderless. There is also bt which will toggle the different border styles.
Examples:
bindsym Mod1+t bn
bindsym Mod1+y bp
bindsym Mod1+u bb
or put in your config file
new_window bb
from: http://i3.zekjur.net/docs/userguide.html (you probably already found that by now )

Client Server Authentication

Hello Coders,
I've written a simple multi threaded client server application. I'm having a bit of a problem developing the application and continually run into a brick wall. The major problem/s I have
1. Is to get the client to register its IP address as a valid user along with the name of the user in order to join the service. I guess am try to implement logon/logoff etc.
2. The application is an online library service.......what "Do I need to check on to" be able to store a number of books and serve and implement requests from the clients?
I tried using the power of the web with no luck and failed to gained worthwhile educative direction. I kindly ask for your assistance. Thanks
By the way, I'm user ServerSocket and don't have any Graphical User Interface implemented

>
1. Is to get the client to register its IP address as a valid user along with the name of the user in order to join the service. I guess am try to implement logon/logoff etc.
>
I'd recommend username/password, because the user should be able to login from another client, shouldn't he?
>
2. The application is an online library service.......what "Do I need to check on to" be able to store a number of books and serve and implement requests from the clients?
>
You have to think about the communication between server and client. This could be everything,... This could be a standard like JMS or even HTTP. You also could, as I recommend for educational purpose, write your own 'protocol'. You could implement it with simple Readers in Writers, as you find in the java.io package. Back in my apprenticeship, our little chat system was using Object In- and OutputStreams.
If you have your technology for your protocol, you have to define it. If you use readers and writers, client could send something like "login username password" and the answer would be "login granted" or "login denied". Or using Object Streams you could send an object like "LoginIn" which holds user/pass and send back a LoginOut which holds something like a loginAccepted:boolean flag.
To store data in a backend, you should check the DAO pattern: http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.html. You can store data in files as serialized objects, xml, etc. Or in a database, such as MySQL -> In this case, you should check sun's jdbc developer guide http://java.sun.com/javase/6/docs/technotes/guides/jdbc/ and hibernate (http://www.hibernate.org).
hope this helped...
regards
slowfly

Client == server - problems with callbacks

Hi everyone!
I'm having trouble establishing bidirectional communication between a client and a server (code samples are below).
Both classes (client & server) extend UnicastRemoteObject and implement Interfaces that are extending Remote. Now the client looks up the server and tries to register itself at the server by calling a method like this:
remote_server.setClient(this);
as long as I execute both programs in the same LAN this method-call works fine, but when client and server connect through internet I'm getting the following exception:
---------------------- Exception ------------------------>
java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
     java.rmi.ConnectException: Connection refused to host: 192.168.0.3; nested exception is:
     java.net.ConnectException: Connection timed out
     at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:292)
<---------------------- Exception ------------------------
maybe helpful:
- 192.168.0.3 is the client's LAN-IP
- I am directly connected to the internet via ADSL-modem (no router)
I searched the forums for several hours now, I read through the following tutorial,
http://developer.java.sun.com/developer/onlineTraining/rmi/exercises/RMICallback/index.html
but still I didn't find a solution.
I already spent a lot of time developing this and I start to get desperate, so I hope someone of you out there can help me!
pilord
==================== Codesamples =======================>
public class ServerImpl extends UnicastRemoteObject implements Server {
Client client;
public ServerImpl() {
LocateRegistry.getRegistry(1096).rebind("test",this);
/* specified in Remote-Interface: Server*/
public void setClient(Client client) {
this.client = client;
public class ClientImpl extends UnicastRemoteObject implements Client {
public ClientImpl() {
Server s = Naming.lookup("rmi://***.***.***.***:1096/test");
s.setClient(this); // HERE is the trouble.
<==================== Codesamples =======================

Don't feel lost, crumb. Http tunnelling is not as complex as it seems. I just started using RMI at my new job here and in a couple of weeks I've already picked up on alot of what I needed to know. (I just posted a question myself on the same topic.) Basically what you have to do is set up a web server for RMI to talk to at the server side. It will work if the webserver is listening on port 80 with the rmiservlet.ServletHandler registered to respond to any path request of cgi-bin/java-rmi.cgi. In other words "cgi-bin/java-rmi.cgi" should be the servlet-mapping of the ServletHandler. The servlet merly acts as a proxy on behalf of the RMI client and fowards the request to the desired port on the server. If you know how to set up a servlet as the default web app then it is really a breeze. On the client side you only need to set the http.proxyHost and http.proxyPort system properties to the appropriate values for your proxy server. (I mistyped these property names in my prior post use what I have here as I just read it out of the RMI book.) Do a search on HTTP tunnelling and you should turn up dozens of hits. I have the source to the servlet if you need it. I've already modified it for my own purposes though it should still work for you. If you forego http tunnelling then you'll have to do a complete app rewrite to use another protocol because RMI just doesn't work through firewalls without it. Alternatively you can get down and dirty with some low level sockets coding (this is what I'm thinking I'll end up doing eventually) to get it working without standard RMI/HTTP but that's way more complex. Unfortunately it looks like your callback code will need to be rewritten unless you either go commercial or do the socket stuff. (There does seem to be a shareware product called rmi doves that would help you here.) I'll be happy to assits you in any way as you need help.
Cliff

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.

Client-Server - SOA.... Is it really a transition or a big development ?

Hi,
In all sources related to SOA/ESA by SAP, it is said that, transitioning from Client-Server Arch(CSA) to SOA is the same as transitioning from Mainframe systems to Client-Server Arch.
If we think about Mainframe and CSA, it is obvious that there had been big differences in that transition. Such as, the INTELLIGENT CLIENT concept had appeared to replace the DUMMY CLIENTS, so this had changed the way of IT Business. There would be a main application providing several functionalities(server) and other applications which want to use those functionalities (clients) would connect to the server using some functionalities on its own (that means a client appliction should also have some functionalities in order to at least connect to the server, so that made them different from the DUMMY clients of the mainframe era)
Now, when I look at the differences between SOA and CSA, I cannot see that incompareble differences.Why ? Let me explain :
- One of the most important differences between SOA and CSA is, SOA is vendor and platform independent, so that any application can call any applications functionality as long as they are using Web Services. That is true. But the question arises here : It is still the case that someone is calling some others' functionalities (services), so there is still a client/server mentality, isn't there and We will still be using several client/server programming languages in order to realize the main functionality of the web services but this will be transparent to the user and the integration. The main difference is, SOA is vendor and platform independent. But I don't think this can be commented as a missing feature of CSA. Because the aim of CSA was to make the clients more intelligent and not to make them vendor/platform independent. And also architectures like CORBA and DCOM have also tried to achieve that independency (even though they have restrictions compared to Web Services, one of the main reasons for this is using Web as a transport/communication protocol) but they are still treated as some extensions on top of CSA because they are using CSA beneath. But if we compare Mainframes and CSA, even though I haven't seen manframe ages, I think it is clear that CSA does not use any architectural functionality of Mainframes. They are completely different.. But is SOA and CSA completely different ?
I agree with all reasons why today business needs sth more agile, more flexible and it is becoming clearer day by day that SOA and Web Services provides this environment, BUT, I still cannot make it clear, WHY it is accepted as a transition from CSA and why it is not treated as a big development over CSA while using the main features of it.
Any comments will be appreciated.
Regards
Ahmet Engin Tekin

Good point..Actually those are the things clearly known but it becomes a bit confusing to build clear sentences when it comes to declare the differences. Anyway, here are my additions :
- Mainframes were centralized systems which had their own hardware architecture as well. All processes/applications were running on 1 central DB/system and everyone in the company had to use the same functionality and interface.
- In time, as a result of business demand, people needed different functionalities/applications regarding different business needs. This could either be done by extending the higly-costed big mainframe systems/softwares OR a new approach had to be developed in order to solve those problems. At this point, (thanks to IBM,Macintosh and Xerox) PC and ethernet concepts had emerged. That was a completely different hardware architecture which allowed less costly systems and also distributing the process load and/or applications to different systems in one landscape (app servers, intelligent clients - 2 tier, 3- tier arch.). Thus, while those were happening on harware side, new communication and programming models/languages emerged on software side. As a result, people started using different applications on different systems according to their needs and thus an efficient solution had been provided to the business need (described above).
To criticise, this was really a big transition. Not only software concepts but also hardware concepts are also changed drastically. Actually, it is not wrong if we say, developments on the hardware side, allowed changes on the software side
- What happened next ? Companies started using so many different applications by different vendors with different business logic and programming models (thanks to CSA). But in times, this has emerged the biggest problem of the CSA era : Integration.
We all know the rest. "Web Services" concept emerged with SOA as well. So that, the boundaries between the systems began to disappear.
So, is this a transition ? Well, yes it is.. The point that made it confusing (at least for me) is that this time there is no hardware transition (yet) but only a transition in software side. But I still insist that the IT transition during Mainframe->CSA was like a revolution (forget what you've left behind) but from CSA to SOA; it is more likely to be an evolution (the next best thing)
Anyone have more comments ?
Regards,
Ahmet

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

OLE Alternatives in Forms 6i Client Server

I'm fishing for some advice and maybe some examples of how to get around an OLE issue that's adversely affecting an upgrade project.
We're currently migrating a Forms 4.5 application to 6i. This application displays MS Word documents (OLE Container) that are stored in the database and uses OLE to open manipulate, and save the documents back to the database. We've come across some serious problems with OLE and 6i that don't look like they'll be fixed any time soon (bug #2615804 in particular).
Since OLE (ActiveX) is not supported a web delivered configuration, we're looking at an alternative to interacting and storing Word documents using a client/server configuration. This will have the added bonus of making the move to web delivery once we decide to go down that path.
Has anyone out there had any good experience with overcoming this OLE problem? It seems like every pre-Forms 9i book out there has touted OLE as a way of interacting with Office tools and now OLE has become a roadblock.
I've had a look at the JACOB example, but that doesn't really help if you're not deploying via the web.

With the beans you've looking at visual stuff : like the look and feel project
With the importer it's more like leveraging java functionality : in my case I've just implemented a call to a webservice on an application server. There is nothing visual here and it's just called via a straight bit of PL/SQL that call my java classes ( however, in that case I could also use UTL_HTTP directly to make the call and thus not bother with java importer - but the database wouldn't allow UTL_HTTP calls :( )
For both of these you'd need to tell forms where to find the JAR file in it's java environment - but you won't have that in c/s
Another way is to load up java code into the database and process it within the database and hide it completely from Forms. I've done this sort of thing loading Apache-FOP into Oracle and creating PDF files in the database (as BLOBS) from XML/XSL also in the database as XMLTYPES.
At least that's my view on how it fits together ... maybe others know more :)
Steve

Which media server protocols enable frame accurate seeking and frame stepping in players?

Hi,
... and thank you in advance for taking the time to respond. I am evaluating different protocls for different client platforms, and I'd like to know the following...
Which media server protocols enable frame accurate seeking and frame stepping in players? (It appears that RTMP does. However, what about HDS? What about HLS?)
Why is it that some do and some don't? (Intuitively, this would seem to be more an issue of the player than the protocol, but then maybe it has something to do with the buffers and the specific information passed to the client.)
For those protocols that do support frame accurate seeking and frame stepping in players, does the addition of Access DRM protection have any effect? (Intuitively, I would say no, but then maybe there are configuration changes needed in AMS to make it work.)
Thanks!

I searched for a DVD player with a jog shuttle -- and you're right. They're all but impossible to find! I havent' found one made in the past 5 years!
I don't know of any way you could accomplish the same thing with software either.
Most DVD players have slow-motion and frame-by-frame features. (Even my cheap $40 Toshiba.) That may be the closest to it.

Authetication problem in client/server app

I am presently developing a client/server program, and I'm wondering what will be the best form of authentication. I plan to develop a protocol for the programs, any deviation leading to socket closure. I thought about signatures, but I don't think any body's ready to vouch for me(ie I don't know how to go about signatures). Is there any help?

Learn about JAAS

Small client server project. deisgn idea good or bad?

Hi,
I have a question:
I have this plan to make a small Swing based GUI on the client machine (that I would like a novice user to be able to double click on to launch) which needs to connect to a Server side component , I am thinking a simple Servlet or JSP page. Then what needs to happen is a few messages are transferred to ascertain the users identity for authenitcation as so:
1. Client -> Server 2. Server -> Client 3. Client -> Server. Access gratned or not for access to restricted web page (imagine inbox e-banking etc)
So the main questions are:
1. Can I make a small Swing based GUI App, NOT an applet as I need to read from the client, that can be easily launched by an idiot ;)
2. Can that small app converse with a Servlet in the manner described above.
3. Kinda like 2. Can the Client App launch a browser window to that when the messages are done the user can then get into the area the server has granted them access to (depending on the messages).
I would really appriciate the help. I have looked about on the internet and in books but I never really got a succinct picture this would be possible.
Thanks!

I have this plan to make a small Swing based GUI on
the client machine (that I would like a novice user
to be able to double click on to launch) which needs
to connect to a Server side component , I am thinking
a simple Servlet or JSP page. That will involve writing an applet.
1. Can I make a small Swing based GUI App, I don't know if you can or not! It's certainly possible...
NOT an applet See above.
as I need to read from the client, That's not a restriction. You can sign your applets.
that can be easily launched by an idiot ;) Once again, that's up to you.
2. Can that small app converse with a Servlet in the
manner described above.Yes.
3. Kinda like 2. Can the Client App launch a browser
window to that when the messages are done the user
can then get into the area the server has granted
them access to (depending on the messages).Yes.
I would really appriciate the help. I have looked
about on the internet and in books but I never really
got a succinct picture this would be possible.It is! Good luck, and happy coding! If you need some resources, check out the following:
The Java� Tutorial - Trail: Creating a GUI with JFC/Swing
The Java� Tutorial - Trail: Writing Applets
Trail: Getting Started - Lesson: The Anatomy of an Applet
Java Applet Tutorials
The Java� Tutorial - I/O: Reading and Writing (but no 'rithmetic)

Client/server socket based application

hi does anyone have example of client/server socket based application using Spring and Maven
where application do the following
Client sends a request with a path to any file on the server
„h Server reads the file and responds back with the content
„h Client outputs the content to the console
am trying to follow this
http://www2.sys-con.com/itsg/virtualcd/java/archives/0205/dibella/index.html
http://syntx.io/a-client-server-application-using-socket-programming-in-java/
am using java 6

i have attempt code but i wht to do the following
client/server socket based application that will read the content of a file and stream the content of the file to the client. The client must simply output the content of the file to the console using System.out. The client must be able to run in a standalone mode (non-network mode) or in a remote mode.
Additionally the client must be designed in a way that i can print the output to a console but must be interchangeable where if requirements change i can persist the response to file or persist the response to a database.
/* Server.java*/
///ifgetBoolen= true then...
import java.io.*;
import java.net.*;
import java.util.*;
import java.sql.*;
public class Server
    static String array[][];
    // STEP 1 a1
    // Server socket
    ServerSocket listener;
    // STEP 1 a2 Client connection
    Socket client;
    ObjectInputStream in;
    ObjectOutputStream out;
    public void createConnection() throws IOException
            System.out.println("\nSERVER >>> Waiting for connection.....");
            client = listener.accept();
            String IPAddress = "" + client.getInetAddress();
            DisplayMessage("SERVER >>> Connected to " + IPAddress.substring(1,IPAddress.length()));
      public void runServer()
        // Start listening for client connections
        // STEP 2
        try
            listener = new ServerSocket(12345, 10);
            createConnection();
              // STEP 3
//              processConnection();
        catch(IOException ioe)
            DisplayMessage("SERVER >>> Error trying to listen: " + ioe.getMessage());
    private void closeConnection()
        DisplayMessage("SERVER >>> Terminating connections");
        try
            if(out != null && in != null)
                  out.close();
                in.close();
                client.close();
        catch(IOException ioe)
            DisplayMessage("SERVER >>> Closing connections");
    public static void define2DArray(ResultSet RS, int Size)
        try
            ResultSetMetaData RMSD = RS.getMetaData();
            DisplayMessage("SERVER >>> Requested arraySize: " + Size);
            if (RS.next())
                array = new String[Size][RMSD.getColumnCount()];
                for (int Row = 0; Row < Size; Row++)
                    for (int Col = 0; Col < RMSD.getColumnCount(); Col++)
                        array[Row][Col] = new String();
                        array[Row][Col] = RS.getString(Col+1);
                        DisplayMessage(array[Row][Col] + " ");
                    RS.next();
            else
                array = new String[1][1];
                array[0][0] = "#No Records";
        catch (Exception e)
            DisplayMessage("SERVER >>> Error in defining a 2DArray: " + e.getMessage());
    public static void DisplayMessage(final String IncomingSMS)
        System.out.println(IncomingSMS);
//client
* @author
import java.io.*;
import java.net.*;
import javax.swing.*;
public class ClientSystem
    static Socket server;
    static ObjectOutputStream out;
    static ObjectInputStream in;
    static String Response[][];
    static boolean IsConnected = false;
    static int Num = 0;
    public static void connectToServer() throws IOException
        server = new Socket("127.0.0.1", 12345);
//        server = new Socket("000.00.98.00", 12345);
        String IPAddress = "" + server.getInetAddress();
        DisplayMessage("\nCLIENT >>> Connected to " + IPAddress.substring(1,IPAddress.length()));
    public static void getStreams() throws IOException
        out = new ObjectOutputStream(server.getOutputStream());
        out.flush();
          in = new ObjectInputStream(server.getInputStream());
          IsConnected = true;
          DisplayMessage("CLIENT >>> Got I/O streams");
    public static void runClient()
        try
            connectToServer();
            getStreams();
              DisplayMessage("CLIENT >>> Connection successfull....\n");
              DisplayMessage("CLIENT >>> Want to talk to server");
        catch (IOException ioe)
            System.out.print("."+Num);
            Num++;
    public static void closeConnection()
        try
            out.close();
            in.close();
            server.close();
        catch(IOException error)
            DisplayMessage("CLIENT >>> Could not close connections");
    public static void Start()
        System.out.print("\nCLIENT >>> Attempting connection.....");
        try
            IsConnected = false;
            while (IsConnected == false)
                runClient();
                if (IsConnected == false)
                    Thread.sleep(100);
        catch (Exception e)
            DisplayMessage("CLIENT >>> Attempting connection.....");
    public static String sendSMS(String sms)
        Response = new String[0][0];
        try
            DisplayMessage("CLIENT >>> " + sms);
            out.writeObject(sms);
            out.flush();
            Response = (String[][])in.readObject();
            DisplayMessage("CLIENT >>> Waiting for server to respond...");
            for (int Row = 0; Row < Response.length; Row++)
                System.out.printf( "_SERVER >>> \t");
                for (int Col = 0; Col < Response[Row].length; Col++)
                    //DisplayMessage( "_SERVER >>> " + Response[Row][Col] + " ");
                    System.out.printf( "%s\t", Response[Row][Col]);
                System.out.println();
            DisplayMessage("CLIENT >>> Query processed successfully....\n");
        catch(ClassNotFoundException cnfe)
            DisplayMessage("CLIENT >>> Class not found for casting received object");
        catch(IOException ioe)
            reConnect();
        catch (Exception sqle)
            DisplayMessage("CLIENT >>> Error sending query ??? " + sqle.getMessage());
        return "transmission successfull";
    public static void reConnect()
        try
            DisplayMessage("CLIENT >>> Connection was lost. Trying to reconnect...");
            closeConnection();
            Thread.sleep(100);
            IsConnected = false;
            while (IsConnected == false)
                runClient();
                Thread.sleep(200);
        catch (Exception e)
            DisplayMessage("CLIENT >>> Error trying to Re-Connect...");
    public static void DisplayMessage(final String IncomingSms)
        System.out.println(IncomingSms);
    System.out.printf("Isms: %s", IncomingSms); ///naah.
    public static String[][] getResponse()
        return Response;
    public static String getResponse(int row, int col)
        return Response[row][col];
how can i do below using above code
The program must be able to work in a non-networked mode. In this mode, the server and client must run in the same VM and must perform no networking, must not use loopback networking i.e: no “localhost” or “127.0.0.1”, and must not involve the serialization of any objects when communicating between the client and server components.
The operating mode is selected using the single command line argument that is permitted.
imust use a socket connection and define a protocol. networking must be entirely bypassed in the non-network mode.

Establish a connection through RF modem's on client & server side & to set up PPP communication for data transfer

hi
can any1 over here help me out in how to establish connection between 2 RF modem's for data transfer , between client & server USing LABVIEW?
I want to establish a connection between 2 PC's through RF modem on client & server side & to set up PPP communication for data transfer.
(I have tried data transfer through RS-232 using TCP/IP whn the 2 PC's are connected over ethernet... which is working.
I also tried connecting loopback cable between 2 PC's COM port & geting data transfer using VIsa configure serial port & other visa functions ... which is working)
can u guide me how to establish connection between 2 RF modem's using LABview?
& how does the data transfer take place between 2 RF modems through RS-232?
is it using TCP/IP?
If you got any links to go abt this issue do send me related links .. or any examples .....
I am currently using Labview version 8.
Waiting in anticipation.. reply ASAP..
thanking you
Regards
Yogan..

Howdy yogan,
Maybe you could clarify a few things for me, and we'll see how we can help ya. TCP/IP protocol occurs through an ethernet connection; RS-232 communication occurs through an RS-232 serial connection, typically through a cable that has a DB9 connector on both ends. Do you mean that the RF modems in question have the option to communicate via RS-232 and/or via TCP/IP ethernet? Specific information like the manufacturer of your RF modems, the model number of your RF modems, and how you connect the modems to the PC would enable us to give you more efficient support.
You can check our Instrument Driver Network (IDNet) to see if a plug-and-play/IVI driver already exists for your RF modem. (You'll need to know its manufacturer and model number.) In the case that you do find an IDNet driver for your modem, you can use this KnowledgeBase article for instructions on how to use the driver.
Another excellent resource to consider is the NI Example Finder. You can access this within LabVIEW by navigating to Help»Find Examples and then searching for serial or TCP/IP examples.
Message Edited by pBerg on 03-10-2008 04:35 PM
Warm regards,
pBerg

Need help in desigining Client/Server Application using Java

Hi,
I am new to Java and no sooner that I started studing it I have been given a project - client server java Application that allows a user to do a property search based on critiras (eg location, price) and display the results. I am stuck because I don't know where I need to start. Have to use IDE (Netbeans or Eclipse) but not sure about dev frameworks.
Can someone give me an outline of what I should do / where I should start? What will be the best solution?
Thanks in adance

http://java.sun.com/docs/books/tutorial/networking/index.html
That's Sun's networking tutorial series. Live it, learn it, love it. You'll need to decide if you want to use connected sockets or datagrams. You'll need details like, can multiple clients connect simultaneously?
The tutorials are the first step though.

Client server protocol book

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